01 -
Heat a heavy skillet over medium heat. Add ground beef and chopped onion, cooking until the beef is no longer pink and crumbled, about 3 to 5 minutes. Drain excess fat.
02 -
Stir pizza sauce, drained mushrooms, sugar, and dried oregano into the cooked beef mixture until fully combined.
03 -
Spoon the meat sauce onto the toasted hamburger buns, then evenly sprinkle shredded mozzarella cheese on top.
04 -
Arrange assembled buns on ungreased baking sheets in a single layer.
05 -
Place baking sheets 10 centimeters from the broiler heat source and broil until cheese is melted and bubbly, approximately 2 minutes.