This French Onion Mac and Cheese is a delicious and unique mash-up of two classic comfort foods. Built for a crowd, it features sweet and savory caramelized onions, a rich and creamy cheese sauce, and a crunchy Panko breadcrumb topping for a lovely combination of flavors and textures. It’s the kind of side dish that will have your guests going back for seconds, perfect for holiday gatherings and other celebratory meals.
Why I love this mac and cheese, and hope you will, too
Carby sides are the stars of the T-day show at Casa SoupAddict. I don’t think this is particularly controversial, because it always seems to me that the big roasted turkey and the carving of it is more for show than anything. Like a grand kick-off to dinner. The sides are what get passed up and down the table all meal long.
Mac & cheese is a fairly new tradition for us, just a few years old. But now I can’t imagine Thanksgiving dinner without it. The first year, it came out of a box. But now it’s a whole thing.
Am I sad about testing mac and cheese for the blog for a whole month? Lol, that would be no. For another unique take on holiday-worthy mac and cheese, check out my Cajun Mac and Cheese.
Reasons French Onion Mac and Cheese is a hit at Casa SoupAddict:
- Combines two comfort food classics: French onion soup and mac and cheese.
- Features deeply caramelized onions for an irresistible savory-sweet flavor boost.
- Perfect for holiday gatherings or special dinners, it serves a crowd with ease.
- Baked with a crispy Panko topping that contrasts the creamy sauce.
- Deliciously creamy and saucy even after baking, with a flavor-packed bite in every forkful.
Main Ingredients, Notes, and Substitutions
Onions — Use one of the sweeter types of onions, as their sugars caramelize better than the sharper varieties. For this dish, I wouldn’t recommend using red onions. Stick with sweet, white, or yellow.
Cheeses — For mac and cheese in general, I like using a mixture of cheeses: something aged, something sharp, and something melty. For the photos in this recipe, you’ll see that I used 4 cheeses, because I happened to have them all in my fridge!
The traditional cheese to use for French Onion soup is Comte, which can be hard to find in some regions. Gruyere is a nice substitute. For the “something melty,” I usually choose fontina. It melts like mozzarella but has a lovely, pronounced flavor. It’s one of my favorite cheeses! Monterey Jack would also be a good choice. And then I always include an extra sharp white or orange cheddar in my mac and cheese.
Can you use Velveeta? Um. Sure. But it wouldn’t be my first choice for a celebration-level dish.
Breadcrumbs — I love the crunch factor of Panko breadcrumbs, especially after they’ve been butter-toasted. Regular breadcrumbs will work, too. I also go for the seasoned variety when available because it adds a little extra hit of flavor along with the crunch.
Dairy — This is already definitely not health food, so I would say, what the heck, and don’t skimp on the fat content of your milk selection: go with whole milk or half and half. You want a nice, smooth, substantial cheese sauce, and you won’t really get there with 2% or non-fat milk.
At the opposite end of the decadence spectrum, heavy cream will be fine, too, but if the resulting cheese sauce is really thick, you might want to thin it a little with a drizzle of water while it’s cooking. Pourable sauce is perfect; goopy sauce is not.
Cook’s Notes
- If you’ve never caramelized onions before, you might be nervous about the huge stack of slices this recipe produces. Don’t worry. Onions are almost 90% water, which evaporates over the course of the slow cook. Your nearly overflowing pan will reduce down to a heaping cup.
- Some cooks will try to convince you that onions can be properly caramelized in 20 to 30 minutes, and, sadly, even some of the big cooking brands try to push clever shortcuts to achieve what only time can accomplish. There is no shortcut, and onions that are cooked in 20 minutes are browned (i.e., seared), not caramelized. Caramelization is a slow process where sugars are slowly released from the onion and carefully heated to sweetness. Not burned.
- And speaking of shortcuts, while we all love a good one, I would encourage you to take the extra time to shred your cheeses fresh from a block of cheese, rather than buying a bag of shredded. Pre-shredded cheeses almost always have preservatives and fillers on board to stave off mold and, frankly, to save the manufacturer some money. When you see “cellulose” in the ingredient list? That’s wood pulp. Yes, it’s edible. But it’s simply not cheese.
How to Make French Onion Mac & Cheese
Ready to make the recipe? Skip to the recipe card now to get the full ingredient list, quantities, prep/cooking times, and detailed instructions. Or, keep scrolling for a visual walk-through of making the dish.
Pre-cook prep notes
- Slice the onions thinly, and perhaps give them a brief chop. You don’t want dice-sized pieces, but you also don’t want long strings that hang off the fork. One- or two-inch lengths are perfect. This can be done ahead of time, even the day before, and stored in the fridge in a bowl.
- Grate the cheeses. This can also be done a day or so in advance.
- You’ll need a total of 6 tablespoons of butter. Slice them into 1 tablespoon pats for their various uses in the recipe.
Step 1: Caramelize the onions
Melt the butter in a large skillet or braiser over medium heat. Add the onions and stir to coat. Let the onions sweat at this heat until they’re soft and translucent, but have no browning. Reduce the heat to low-medium, and let the onions cook for another 50 to 60 minutes.
Stir often. Add dissolved beef boullion paste — another nod to French onion soup — to the pan if things seem to be drying out. The onions reduce and caramelize by releasing moisture and sugars, but at the same time, they have to stay moist on the outside, or they will singe on their edges.
When the onions are deeply golden and jammy soft, they’re ready to use. Turn off the heat and hold.
Step 2: Cook the macaroni
While the onions are caramelizing, start on the mac and cheese.
Cook the macaroni in a large pot of boiling water, according to package directions. Drain, return to the pot, and set aside.
Step 3: Make the cheese sauce
Melt 3 tablespoons of the butter in a medium pot over medium heat. Stir in the flour to create a loose paste (e.g., a blonde roux).
Begin stirring or whisking in the dairy a little at a time until completely smooth. Raise the heat and allow the sauce to thicken, stirring frequently – it should coat the back of a spoon. Mix in the Worcestershire sauce and some pepper.
Set aside one cup of the shredded cheese, and then mix the remaining into the sauce a little at a time until fully incorporated.
Step 4: Assemble the mac and cheese
Fold the onions into the macaroni, followed by the cheese sauce. You can do this either in the pot in which you cooked the pasta, in a separate large bowl, or in the baking pan, although it’s harder to thoroughly stir things in the baking pan. I transferred the macaroni to a very large bowl to make sure there was enough room for everything.
Pour the macaroni mixture into the prepared baking dish and smooth out evenly. Cut one tablespoon of butter into small cubes and distribute them throughout the macaroni. Top with the reserved cup of shredded cheese.
Step 5: Make the breadcrumb topping and bake
Melt the remaining tablespoon of butter in the skillet that cooked the onions and pour the breadcrumbs on top of the butter. Stir and cook for a minute or two until the breadcrumbs are a light golden color. Sprinkle evenly over the mac and cheese.
My personal preference is a light coating of Panko — just enough to add a little crunch. If you want an actual cap of breadcrumbs, double the amount in the recipe.
Bake for 25 to 30 minutes, or until the mac and cheese is lightly bubbling in spots. Remove, sprinkle with the thyme leaves and let rest for a few minutes before serving.
Storing
Leftover French Onion Mac and Cheese can be kept in the refrigerator for a few days. Keep in mind that the pasta will inevitably dry out some, in terms of sauciness. I feel like it’s part of the charm of leftover mac and cheese, that you can cut a slice like it’s lasagna. If that’s not your thing, you could try heating a slice in the microwave topped with a little butter and shredded cheese.
But really, this cold and more solid state is where you can experiment with mac and cheese on other things. As in, slice it thick and make a grilled cheese sandwich out of it. Or wrap it up in a burrito with some leftover turkey. Or break it up and add it to an omelet or a frittata with onions and peppers.
Can French Onion Mac and Cheese be made ahead?
Yes. It’s usually not optimal to stash pasta dishes in the fridge for a holding period, because they continue to absorb the liquids around them (which would include the cheese sauce) and get a bit soft and less saucy.
However, you can do part of the recipe ahead and save a little bit of time. I recommend preparing the recipe through the step where you combine the cooked macaroni with the caramelized onions and cheese sauce, reserving about a cup of the cheese sauce and storing it separately in the fridge. If you have the room, you can even pour the macaroni mixture into the baking dish, cover, and store the baking dish in the fridge.
Then, when you’re ready to bake, mix in the remaining cheese sauce — warmed a little to loosen — and top with the pats of butter and the Panko crumbs, and then bake. After baking, you can wrap the dish thoroughly in foil to hold the heat, if you need a little more time to get the rest of your meal completed and on the table.
Another approach would be to cook just the onions ahead of time — even days before — and store them in the fridge. Grate the cheeses ahead of time, too, and you’ll have a great head start on the dish.
As a huge fan of mac & cheese in general, I whole-heartedly endorse it as fit for special celebrations. French Onion Mac and Cheese takes a common dish and adds a special, unexpected twist that I hope your family and guests will love.
French Onion Mac and Cheese Recipe
Ingredients
For the onions
- 1 tablespoon butter
- 5 cups sliced onions (about 3 small, 2 medium)
- 1/2 teaspoon beef Better than Bouillion paste
- 1/2 cup water
For the mac and cheese
- 1 pound elbow macaroni (or other small pasta, such as shells)
- salt
- 3 tablespoons butter
- 3 tablespoons all-purpose flour
- 3 cups whole milk or half and half
- 4 cups shredded cheeses (such as Gruyere, sharp white, smoked gouda, fontina)
- 1 teaspoon Worcestershire sauce
- salt and black pepper
For the topping
- 2 tablespoons butter
- 1/2 cup Panko bread crumbs
- Fresh thyme leaves
Instructions
For the onions
- In a large skillet, heat butter over medium until melted. Add the onions and stir to coat. Let the onions sweat, stirring frequently, for about 10 minutes, or until they begin to soften, but remain white and translucent.
- Reduce heat to medium-low and continue to cook the onions, over the next 50 minutes. In a small bowl, stir the boullion paste into 1/2 cup of very hot water until it’s fully dissolved and keep near the stove. The onions will reduce as they release more moisture and begin to take on golden hues. Keep an eye on everything, stirring often, and don’t let the onions dry out and begin to brown on their edges. If they do, reduce the heat further and add a teaspoon or two of the boullion liquid to the pan, mixing well with the onions to keep them moist.
- When the onions are golden, very reduced, and seem almost melty, they’re finished. Reduce heat to low to hold until ready to use.
For the mac and cheese
- Preheat the oven to 375ºF, and rub the interior of a 13×9″ baking pan with butter or oil to minimize sticking.
- Cook the elbow macaroni in a large 3-quart pot according to the directions on the box. While the pasta cooks, make the cheese sauce.
- In a medium pot, heat 3 tablespoons of butter over medium until melted. Stir the flour and let heat for a minute to cook off the rawness of the flour. Stir in the dairy one cup at a time, whisking to create a smooth, lump-free texture. Increase heat to medium high and let the sauce base bubble and thicken. When the sauce clings easily to the back of a spoon, stir in 3 cups of the shredded cheese (reserving 1 cup for the topping), a handful at a time, incorporating it completely before the next handful. When the cheese sauce is smooth, stir in the Worcestershire sauce and a big pinch of black pepper.
- When the pasta finishes cooking, drain completely and return to the pot.
- Fold the caramelized onions into the pasta, followed by the cheese sauce.
- Pour the pasta into the prepared baking pan and even out the top. The onions may or may not be visible — that’s okay. They’re there for flavor, not for bling!
Make the breadcrumb topping and bake
- Melt one tablespoon of the butter in the skillet that cooked the onions. Pour the Panko bread crumbs over the melted butter and stir until golden (just a couple of minutes).
- Cut the remaining tablespoon of butter into small cubes and position around the mac and cheese, and distribute the cup of shredded cheese.
- Sprinkle the breadcrumbs evenly over the mac and cheese.
- Bake for 25 to 30 minutes, or until the mac and cheese is bubbly or sizzling. Remove from the oven and let rest for a few minutes before serving. Sprinkle fresh thyme leaves over the topping.