In a large skillet, heat a drizzle of olive oil over medium heat. Add chopped onions, carrots, and celery, sautéing until soft—approximately 5 minutes. Then, stir in the ground beef and Italian sausage, cooking until browned. Add minced garlic, dried oregano, and red pepper flakes, letting them infuse for about 1 minute. Pour in tomato paste and puréed tomatoes, simmering gently for 15 minutes until thickened.

In a mixing bowl, combine ricotta cheese, a splash of milk, eggs, grated Parmesan, shredded mozzarella, and chopped fresh parsley. Blend thoroughly until creamy and well-integrated.

In a 9x13 inch baking dish, spread a thin layer of the prepared meat sauce on the bottom. Place dry lasagna noodles over the sauce, overlapping slightly. Spoon half of the ricotta mixture over the noodles, spreading evenly. Repeat this layering process with more meat sauce and noodles, until you create a total of three layers, finishing with a generous layer of meat sauce on top.

Sprinkle the remaining shredded mozzarella and grated Parmesan evenly over the top layer of meat sauce. Cover the dish tightly with aluminum foil.

Preheat your oven to 375°F (190°C). Bake the lasagna for 45 minutes with the foil in place. After 45 minutes, carefully remove the foil and bake for an additional 20 minutes, until the cheese is bubbling and golden-brown.

Once out of the oven, allow the lasagna to rest for 10-15 minutes before slicing.