In a large skillet over medium heat, warm 2 tablespoons of olive oil. Add 1 finely chopped onion and sauté until translucent, about 5 minutes. Stir in 2 minced garlic cloves, cooking for an additional minute. Add 1 pound each of ground beef and Italian sausage; cook until browned, approximately 8-10 minutes. Drain any excess fat, then mix in 28 ounces of crushed tomatoes, 2 tablespoons of tomato paste, 1 tablespoon of sugar, and season with 1 teaspoon of dried basil. Simmer the sauce for 20-25 minutes, stirring occasionally.

In a mixing bowl, combine 15 ounces of ricotta cheese, ½ cup of sour cream, 1 beaten egg, ½ cup of grated Parmesan, and 1 tablespoon of chopped parsley. Mix thoroughly until smooth and creamy.

Preheat your oven to 375°F (190°C) while you grease a 9×13 inch baking dish. Begin layering your lasagna by spreading a thin layer of meat sauce at the bottom of the dish. Place 3-4 lasagna noodles on top, followed by half of the ricotta mixture and a portion of shredded mozzarella. Repeat this layering process until all ingredients are used, finishing with a layer of noodles topped with meat sauce, mozzarella cheese, and a few pats of butter.

Cover the assembled lasagna tightly with aluminum foil and bake in the preheated oven for 30 minutes. Remove the foil to allow the cheese to melt and brown for an additional 15-20 minutes.

Once baked, carefully remove the lasagna from the oven and let it rest for 15 minutes before slicing. Garnish with extra chopped parsley.