Pulse half an onion in food processor.
Make burger patties: Combine ground beef (80/20), onion, and Worcestershire sauce, and form into 1/4 lb. patties. Add salt and pepper to the outside this should help form a crust in the air fryer. Add the patties to the air fryer for 14 to 15 minutes.
Make gravy: Slice onions into half moons and cook down with oil until translucent. Slice whole mushrooms lengthwise and add to onions. Sauté until tender, then add in beef stock. Bring to a boil then reduce to simmer. Add in 1/4-1/2 can
Campbell’s® Cream of Mushroom Soup (this also acts as the thickening agent for the gravy and more of the mushrooms will add extra umami!). Add Worcestershire and soy sauce to taste, and once burgers are done in air fryer, smother in gravy.