Bring bottled clam juice and potatoes to boil in heavy large saucepan over high heat. Reduce heat to medium-low; cover and simmer until potatoes are fork tender, about 10 minutes. Remove from heat.
Heat butter and oil in heavy large stock pot over medium heat. Add bacon and cook until it begins to brown, about 8 minutes or so. Add onions, celery, garlic, carrots, thyme and bay leaf and sauté until vegetables soften, about 6 minutes. Stir in flour and cook 2 minutes to remove the raw flour flavor. (Note: I always find that 1/4 cup of flour is not enough, but 1/3 cup is too much. Usually, a heaping 1/4 cup is just about right).
Gradually add reserved juices from clams, whisking thoroughly. Allow to heat for a few minutes to thicken. Add some (or all of thpotatoes from the potato/clam mixture. Use an immersion blender to smooth out the chunks of vegetables. (It doesn't need to be completely velvety - simply blend to your preferred texture. I like to leave small lumps of onions, celery and carrots visible.)
Add the rest of the potato mixture (including liquid), clams, half-and-half or cream, fish sauce*, Worcestershire sauce and hot pepper sauce. Simmer chowder 5-10 minutes to blend flavors, stirring frequently (do not allow to boil or the cream will curdle). Season to taste with salt and pepper.
(Can be prepared 1 day ahead. Refrigerate uncovered until cold, then cover and keep refrigerated. Bring to simmer before serving.)*So, what's with the fish sauce? Isn't the clam juice enough? Yes and no. Clam juice is a fairly mild by-product, compared to other sea creatures (think, salty sardines). Folks mix it with tomato juice and drink it right down. It's not my cup o' tea, but, there's even a brand of juice drink you can buy at the grocery store called Clamato. Fish sauce, however, is much stronger than clam juice. I personally avoid even sniffing the bottle of fish sauce; however, when added to food while cooking, it imparts an incredible umami that you just can't get from anything else. SoupAddict recommends fish sauce.
New England Clam Chowder was originally published on https://soupaddict.com/new-england-clam-chowder/