Heat the Instant Pot insert on the sauté and add the ground beef.
Brown, stirring and crushing into small pieces with a wooden spoon.
Strain any excess fat off (I did not have excess fat using 85/15 ground beef).
Add the onion, garlic and mushrooms and cook 3-5 minutes, until mushrooms have started to release some liquid.
Add the remaining ingredients, except the sour cream and parsley, and stir together.
Pressure cook on high for 2 minutes. Use the quick release to release the pressure.
Stir in the sour cream and serve hot garnished with parsley.
If too thin, simmer for a few minutes to allow excess moisture to evaporate. You can also use a cornstarch slurry to thicken (mix 1 tablespoon cornstarch with 1 tablespoon water and slowly stir in while whisking - just a little at a time).
Omit the mushrooms if you prefer not to use them.
You can substitute chicken stock for beef stock if needed.
If you like a touch of spice (not traditional) I like to add a little spicy paprika.