Preheat oven to 350°F. Cook mostaccioli pasta in salted boiling water until al dente. Drain and set aside.
In a large skillet, brown Italian sausage with cooking oil over medium heat. Add diced onion and minced garlic; sauté until fragrant.
Stir in Italian seasoning, garlic powder, salt, black pepper, tomato paste, crushed tomatoes, diced tomatoes, and sugar. Simmer for 3 minutes.
In a bowl, combine ricotta, 1/2 cup shredded mozzarella, 1/4 cup grated parmesan, chopped parsley, salt, black pepper, and egg for the cheese filling.
Assemble in a 9x13-inch casserole dish: layer half of the pasta with meat sauce, then the cheese filling, then the remaining pasta with meat sauce.
Sprinkle with 1 cup shredded mozzarella and 1/4 cup grated parmesan cheese. Bake for 25-30 minutes, or until bubbly and golden.