Heat the butter in a 4 or 5 quarter soup pot or Dutch oven over medium. Add the onions when the butter has melted and saute until soft.

Add the mushrooms. Stir well to mix with the butter and onions. Cover with a lid to concentrate the heat and help the mushrooms give off their liquids faster.

When the mushrooms have softened and browned, stir in the sherry, and let cook for several minutes to cook off the alcohol.

Mix in the dill, salt, and paprika.

Increase the heat to medium-high and add the chicken broth and Worcestershire sauce.

When the liquids come up to a light simmer, add the cornstarch to a medium mixing bowl and add several ladles of hot soup. Whisk until smooth, then pour into the pot.

Adjust the heat so that the soup remains at a gentle simmer and does not reach a boil. Cook for 15 minutes to give the cornstarch time to thicken the soup. Stir frequently, making sure the mushrooms don’t stick to the bottom.

You’ll notice a change in the consistency of the soup as it begins to take on a thin gravy quality.

Reduce heat to low, and wait for the bubbling to completely stop.

Whisk together the half and half and the sour cream. Add two ladles of hot soup and whisk until smooth. Stir into the soup, mixing thoroughly. The soup broth should be smooth with a little body.

Stir in about half of the lemon juice, along with a big pinch of salt. Taste the soup. Add the remaining lemon juice and more salt if desired.

Sprinkle the parsley over the soup, and serve immediately with extra sour cream as a topping.