Heat A Large Skillet Over Medium-High Heat And Cook And Stir The Ground Beef Until The Meat Is Crumbly, Evenly Browned, And No Longer Pink. Drain And Discard Any Excess Grease. Transfer Ground Beef To A Bowl; Set Aside. Cook And Stir The Cabbage, Onion, Carrots, And Mushroom In The Skillet Over Medium-High Heat Until The Vegetables Are Tender, 5 To 7 Minutes. Stir In The Beef, And Season With Salt And Pepper. Fill Each Pita Half With The Hot Cabbage Mixture. Top With Mozzarella Cheese.