Step 1: In a large Dutch oven or heavy-bottomed pot, heat 2 tablespoons of olive oil over medium-high heat. Add 1 pound of ground beef and 1 pound of Italian sausage (casings removed, if applicable). Break up the meat with a spoon and cook until browned, about 8-10 minutes. Drain off any excess fat.
Step 2: Add 1 large chopped yellow onion and 4 cloves of minced garlic to the pot. Sauté until the onion is softened and translucent, about 5-7 minutes. Add 1 teaspoon of dried oregano, 1/2 teaspoon of dried basil, and a pinch of red pepper flakes (optional) and cook for another minute until fragrant.
Step 3: Stir in 2 (28 ounce) cans of crushed San Marzano tomatoes, 1 (6 ounce) can of tomato paste, 1 cup of beef broth, 2 tablespoons of sugar, 1 teaspoon of salt, and 1/2 teaspoon of black pepper. Bring the sauce to a simmer, then reduce heat to low, cover, and let it gently simmer for at least 1 hour, or up to 2-3 hours for deeper flavor. Stir occasionally.
Step 4: In a large bowl, combine 32 ounces of whole milk ricotta cheese, 1 cup of freshly grated Parmesan cheese, 2 large eggs, 1/4 cup of chopped fresh parsley, 1 teaspoon of salt, and 1/2 teaspoon of black pepper. Mix thoroughly until well combined.
Step 5: Bring a large pot of salted water to a rolling boil. Add 16 ounces of lasagna noodles (if not using oven-ready). Cook according to package directions until al dente. Drain well and lay them out on a clean surface or parchment paper to prevent sticking.
Step 6: Preheat your oven to 375°F (190°C). Lightly grease a 9×13 inch baking dish. Spread about 1.5-2 cups of meat sauce on the bottom of the dish.
Step 7: Arrange a single layer of cooked lasagna noodles over the sauce, slightly overlapping if necessary.
Step 8: Spread half of the ricotta cheese mixture evenly over the noodles. Then, sprinkle generously with about 2 cups of shredded mozzarella cheese.
Step 9: Top the mozzarella with another layer of meat sauce (about 1.5-2 cups).
Step 10: Repeat the layering: noodles, remaining ricotta mixture, another 2 cups of mozzarella, and another layer of meat sauce.
Step 11: For the final layer, place noodles on top, cover with the remaining meat sauce, and sprinkle generously with the remaining shredded mozzarella and 1/2 cup of freshly grated Parmesan cheese.
Step 12: Cover the baking dish tightly with aluminum foil (you might want to spray the underside of the foil with cooking spray to prevent cheese from sticking). Bake for 25 minutes.
Step 13: Remove the foil and continue baking for another 20-25 minutes, or until the cheese is golden brown and bubbly. If desired, broil for 2-3 minutes for extra browning, watching carefully.
Step 14: Remove from the oven and let it stand for at least 15-20 minutes before slicing and serving. This allows the layers to set.