Bring a large pot of salted water to a boil. Add the ziti and cook until very al dente, slightly undercooking it since it will finish in the oven. Drain, return to the pot, and set aside.
1½ lbs ziti noodles
Preheat the oven to 425°F and position the rack in the center.
In a large sauté pan over medium-high heat, cook the crumbled sausage until lightly browned and just cooked through. Transfer the sausage to a plate with a slotted spoon, leaving about a tablespoon of fat in the pan. If needed, add a drizzle of olive oil.
1½ lbs ground spicy or sweet Italian sausage
Reduce the heat to low and add the minced garlic and diced onion, stirring constantly until softened but not browned. Pour in the crushed tomatoes and season with salt, sugar, and red pepper flakes. Let the sauce simmer uncovered for about ten minutes.
1 medium onion, 4 cloves garlic, 1 28-oz can crushed tomatoes, 1 teaspoon salt, 2 teaspoons sugar, ¼ teaspoon crushed red pepper flakes
Stir in the cream, grated cheese, cooked sausage, and chopped basil. Pour the sauce into the pot with the pasta and gently mix until evenly coated.
1 cup heavy cream, ⅓ cup grated Parmigiano Reggiano cheese, ⅓ cup chopped fresh basil
Spread half of the pasta mixture into a 9x13-inch baking dish. Tear the fresh mozzarella into bite-sized pieces and scatter them over the first layer. Add the remaining pasta on top, then finish with a layer of shredded mozzarella and a sprinkle of grated cheese.
8 oz whole milk mozzarella cheese, 1 cup shredded mozzarella cheese
Bake uncovered until the cheese is melted and golden brown, about 15 to 20 minutes. Garnish with fresh basil and serve warm.