Set instant pot to saute mode. Add in onions and beef. Saute until beef is lightly browned on the outside. Skip browning the steak if using leftover steak.
Turn off saute mode. Add in diced potatoes, mushrooms, and bay leaves. Pour in beef broth and about 2 to 3 cups water to max fill line in a 6 quart pot. In an 8 quart pot you won't hit the fill line. Eye ball this to make sure there is enough liquid. If you feel you need more water add some.
Stir in salt and pepper. Set the valve to seal then put on high pressure for 20 minutes. Once the pot stops counting release the pressure. Serve with buttered bread.