Step 1

Turn on a multi-functional pressure cooker (such as Instant Pot®) and select Saute function. Heat butter until melted. Saute onion for 2 to 3 minutes. Add garlic and cook for 1 to 2 minutes more. Add mushrooms and saute for 2 to 3 minutes more.

Step 2

Stir chicken broth, sherry, thyme, Worcestershire sauce, salt, and pepper into the pot. Close and lock the lid. Select Manual function; set timer for 5 minutes. Allow 10 to 15 minutes for pressure to build.

Step 3

Release pressure using the natural-release method according to manufacturer's instructions, about 10 minutes. Release remaining pressure carefully using the quick-release method. Unlock and remove the lid.

Step 4

Select Saute function again to bring the soup to a light simmer. Whisk flour into heavy cream. Slowly add cream mixture to the simmering soup, whisking constantly until thickened, 2 to 3 minutes. Turn pressure cooker off. Season soup with additional salt and pepper if desired.