1/2 lb oven ready no-boil lasagna noodles
2 large bunches of fresh spinach, trimmed, cooked, drained and finely chopped
2 cups shredded mozzarella
1/4 cup freshly grated Parmesan cheese
1 lb ground beef
1/2 lb sweet Italian pork sausage, casings removed
1 cup sliced button or cremini mushrooms
2 tsp vegetable oil
1 onion, finely diced
1 carrot, finely diced
1 stalk of celery, finely diced
4 cloves garlic, minced
2 tsp dried oregano
1 pinch hot pepper flakes
1 28 oz can San Marzano tomatoes, undrained
1 14 oz can tomato sauce
1/4 tsp pepper
1/4 tsp Kosher salt
Three Cheese Filling:
2 large eggs, beaten
1/4 tsp fresh cracked black pepper
1/4 tsp fresh ground nutmeg
2 cups ricotta cheese
1 cup shredded mozzarella cheese
1/2 cup freshly grated Parmigiana-Reggiano
Preheat oven to 375°F. In a Dutch oven or large pan, cook the beef over medium-high heat, breaking it up with the back of wooden spoon until the meat is no longer pink, about 6-8 minutes. Using a slotted spoon, transfer it to a plate, and discard the fat. Then add the sausage and cook, stirring occasionally to break up the meat until browned, about 6-8 minutes then transfer to the plate with the beef, and discard the fat.
Pour 1 teaspoon of oil to the pan and add the onions, carrot, celery, garlic, oregano and hot pepper flakes, and stir until they become softened, about 6 to 8 minutes. Meanwhile, sauté the mushrooms in a small skillet with another teaspoon of oil over medium heat, and cook until golden, about 8 minutes. Add the tomatoes, tomato sauce and browned meats to the vegetables, and bring to boil. Reduce the heat and simmer, breaking up tomatoes while stirring frequently, for 20 to 25 minutes or until thickened. Add the mushrooms and season with salt and pepper.
In a medium bowl, mix the eggs, pepper and nutmeg, then blend in the ricotta cheese, mozzarella and Parmesan cheese, stirring well then set aside.
Spread 1 cup of the meat filling on the bottom of a greased 13"x 9" baking dish. Top with one-third of the noodles in a single layer, then spread with 1/3 of the remaining meat filling, followed by half of the cheese mixture, then half of the spinach. Alternating the direction of the noodles from one layer to the next, repeat the layering process one more time.
Finish by topping with the remaining noodles, then spread with the remaining meat filling. Sprinkle generously with the mozzarella and Parmesan cheese. Cover the dish loosely with aluminum foil, and bake for 25 minutes. Then uncover and bake for another 25-35 minutes, until bubbly and heated through. Let stand for 10 minutes before serving.