Preheat oven to 400°F. Grease a 9x13 inch casserole dish with cooking spray. Set aside.
Add ground beef, onions, garlic and mushrooms to a large skillet over medium-high heat. Cook until onion is softened and meat is cooked (about 7 to 8 minutes). Turn off the heat. Stir in pasta sauce.
Spread meat mixture on the bottom of the casserole dish. Cover with a layer of cottage cheese. Top evenly with a layer of frozen Tater Tots.
Bake for 40 minutes. Remove from oven and top with cheese and Italian seasoning. Put back in the oven to bake an additional 5 minutes, or until cheese is melted. Serve hot.