Begin by making the marinara sauce: In a large sauce pan, heat the olive oil over medium heat and add the chopped onion. Cook until the onion is translucent then add the garlic to the pan. Cook for a minute then add the ground beef and ground sausage. Stir the meat and break it up into small pieces using your spoon or spatula.
Once the meat has browned, add the tomato paste and canned tomatoes to the sauce pan. Stir to combine. Add the salt, pepper and dried basil then lower the heat and cook the sauce for 15-20 minutes. Stir occasionally. Set aside once cooked
In a medium bowl, combine the ricotta, heavy cream, Parmigiano-Reggiano and grated mozzarella.
Place about 1/4 cup of the marinara in the bottom of a 9x13 casserole dish. Place 1/3 of the cooked ziti in the dish and top with 1/3 of the sauce and 1/3 of the cheese mix. Repeat this layering process until all of the ingredients are layered into the casserole pan.
Top the ziti with the remaining mozzarella slices and sprinkle with extra Parmigiano-Reggiano.
Bake in a 450 degree F oven for about 30 to 40 minutes or until the cheese on top is melted and browning and the sauce around the edge of the pan is bubbling. Enjoy immediately or freeze!