On 6-quart Instant Pot®, select SAUTE; adjust to normal. Melt butter in insert. Add half of beef strips; cook 6 to 8 minutes or until beef is just browned, turning once. Using slotted spoon, transfer to medium bowl. Repeat with remaining half of beef; transfer to bowl with browned beef. Add onions, mushrooms, salt and pepper to insert; cook 8 to 10 minutes or until softened and browned. Stir in garlic and broth; heat to simmering, stirring constantly. Stir in soup and beef. Select CANCEL.