01 -
Heat a heavy-bottomed skillet over medium-high heat. Add vegetable oil and swirl to coat the pan. Add beef stew meat, breaking it into smaller pieces. Season with black pepper. Sear meat for 1 to 2 minutes on each side until it develops a brown crust but is not fully cooked, then remove from heat.
02 -
Spray the bottom of a 5-6 quart slow cooker with non-stick spray. Arrange sliced onions evenly on the bottom.
03 -
Evenly add seared beef on top of the onions. Sprinkle Au Jus sauce mix over the beef, followed by the beef onion soup mix. Pour French onion soup evenly over the layers. Distribute sliced butter on top.
04 -
Cover and cook on low for 4 to 6 hours, or until beef is tender.
05 -
About 30 minutes before cooking is complete, sprinkle shredded mozzarella and provolone cheese evenly over the beef. Cover and allow the cheese to melt before serving.