Stuffed Peppers: Cut bell peppers in half, remove the seeds, and fill them with your leftover lasagna filling, and cooked ground beef, and top with marinara sauce. Bake until the peppers are tender, and the filling is heated through.
Quesadillas: Spread lasagna filling between two tortillas, add some additional cheese if you like, and heat on a skillet until the cheese is melted and the tortillas are crispy.
Frittata: Whisk together eggs, lasagna filling, bacon, and diced vegetables. Pour into a baking pan and bake at 350F until the eggs are set and slightly browned.
Lasagna Soup: Sauté some onions and garlic in a pot; add canned tomatoes, broth, herbs, and your leftover lasagna filling. Bring to a boil and add crushed lasagna noodles. Simmer until heated through, and the pasta is cooked. Serve with a sprinkle of cheese on top.
Stuffed Mushrooms: Remove stems from large portobello mushrooms, fill with the lasagna filling and cooked ground sausage. Top with parmesan cheese and bake until the cheese is melted and the filling is heated through.
Lasagna Nachos: Spread tortilla chips on a baking sheet, sprinkle the lasagna filling over the chips, top with mozzarella cheese, marinara sauce, and bake until the cheese is melted.
Lasagna Calzone: Roll out pizza dough into a large circle, spread the leftover lasagna filling on one half of the dough, add sauce and your favorite toppings, then fold the other half over the filling, seal the edges, and bake until golden brown.
Savory Pancakes: Mix the lasagna filling with some pancake batter. Cook small portions on a hot griddle until bubbles form on top, then flip and cook until golden brown.
Stuffed Zucchini Boats: Cut zucchini in half lengthwise and scoop out the seeds to create a "boat." Fill with the leftover lasagna filling and ground beef. Top with marinara sauce and parmesan cheese. Bake until the zucchini is tender.
Arancini: Combine the lasagna filling with leftover risotto or cooked rice. Form into small balls, coat in breadcrumbs, and fry until golden brown.