Preheat your oven to 375 degrees F (190 degrees C).
In a large skillet, brown the ground beef with the chopped onion. Drain off any excess grease.
Stir in the minced garlic, crushed tomatoes, tomato paste, mushrooms (if using), oregano, basil, salt, and pepper. Simmer for about 15 minutes, stirring occasionally.
While the sauce simmers, cook the lasagna noodles according to package directions. Drain well.
In a medium bowl, mix together the ricotta cheese, egg, and Parmesan cheese.
Spread a thin layer of the meat sauce in the bottom of a 9×13 inch baking dish.
Arrange three lasagna noodles over the sauce.
Spread half of the ricotta cheese mixture over the noodles.
Sprinkle one-third of the mozzarella cheese over the ricotta mixture.
Spoon about one-third of the remaining meat sauce over the mozzarella.
Repeat the layers: noodles, the rest of the ricotta mixture, another third of the mozzarella, and another third of the meat sauce.
Top with the remaining noodles, the rest of the meat sauce, and the remaining mozzarella cheese.
Cover the baking dish with aluminum foil.
Bake for 25 minutes.
Remove the foil and bake for another 20-25 minutes, or until the cheese is bubbly and golden brown.
Let the lasagna rest for 10 minutes before serving.
Notes
You can add other vegetables like bell peppers or zucchini to the sauce.
For a richer flavor, use a mix of beef and Italian sausage.
Ensure your oven is fully preheated for even cooking.
Nutrition
Serving Size:1 slice
Calories:Approximately 450-550 (will vary based on ingredients)