Step 1

Over medium heat, melt two tablespoons of the butter in a saucepan. Toss in the onion and cook until soft but not browned.

Step 2

Toss in the remaining butter and then add the mushrooms. Cook for 8 minutes.

Step 3

Pour in the chicken stock, add the parsley, and bring to a boil. When bubbling, reduce to a simmer and cook for an hour.

Step 4

Pour soup into a blender (you might need to do this in stages), and process until smooth. Return to the saucepan and bring to a simmer. Pour in the sherry, and season with salt and pepper.