Prepare the mac and cheese according to directions on the package.
2 boxes queso blanco Velveeta shells & cheese
While the pasta's cooking, add the butter to a large skillet set over medium hot. Once the butter's melted add the beef, pepper, onions, and seasonings to the skillet. Cook, stirring often, until the pepper and onion have softened.
1 lb shaved beef, 1 large green bell pepper, 1 yellow onion, 2 tbsp butter, 1- 1 1/2 tbsp Montreal steak seasoning, pinch garlic powder
Stir 1 1/2 cups of mozzarella cheese into the hot mac and cheese until melted. Then add the beef mixture, stirring to evenly combine.
2 cups shredded mozzarella cheese
Transfer the mixture to a greased 2 quart casserole dish, and spread out in an even layer. Sprinkle the rest of the cheese evenly out overtop.
Bake at 350° for 15-20 minutes, just until the dish is hot & bubbly and the cheese has melted.
Broil, if desired, to brown the top. Serve warm & enjoy!