Bring a large pot of salted water to a boil. Add the 12 lasagna noodles and cook until al dente, about 8-10 minutes. Drain the noodles and lay them flat on a sheet of parchment or a clean kitchen towel to prevent sticking.
Heat the olive oil in a large skillet over medium heat. Add the chopped onion and cook until translucent, about 3-4 minutes. Stir in the minced garlic and cook for an additional minute until fragrant.
Add the ground beef and ground turkey to the skillet. Cook, breaking up the meat with a spoon, until browned and cooked through, about 7-8 minutes. Drain any excess fat if necessary.
Pour in the crushed tomatoes and tomato sauce, then stir in dried basil, oregano, salt, and pepper. Simmer the sauce on low heat for 20-25 minutes, allowing the flavors to meld beautifully.
In a mixing bowl, combine the ricotta cheese and egg until smooth and well mixed. This mixture will add creaminess and help bind the layers together.
Preheat your oven to 375°F (190°C). In your deep baking dish, spread a thin layer of meat sauce on the bottom to prevent sticking.
Place 3 to 4 lasagna noodles over the sauce, slightly overlapping as needed. Spread one-third of the ricotta mixture over the noodles, followed by one-third of the meat sauce. Sprinkle with one cup of shredded mozzarella and a bit of grated Parmesan.
Repeat the layering process two more times: noodles, ricotta mixture, meat sauce, mozzarella, and Parmesan. Finish with a final layer of noodles topped generously with meat sauce and the remaining mozzarella and Parmesan cheese.
Cover the baking dish tightly with aluminum foil and bake for 40 minutes. Remove the foil and bake for an additional 15-20 minutes, or until the cheese is bubbly and golden brown.
Let the lasagna rest for about 15 minutes before slicing to allow it to set perfectly.
Sprinkle fresh basil leaves on top for a bright, herbaceous finish. Serve hot and enjoy the comforting layers of your homemade deep dish lasagna.