Step 1

Preheat oven to 350°F. Crumble the meatballs into small pieces using a fork or food processor.

Step 2

Heat crumbled meatballs in a skillet set over medium heat for 2 minutes. Season meatballs with crushed red pepper flakes and salt and black pepper to taste. Stir sauce into meatballs and heat to a simmer for 5 minutes.

Step 3

In a baking dish, cover the bottom of the dish with half of the sauce. Add the manicotti to the baking dish and cover the top of the manicotti with remaining sauce and mozzarella cheese.

Step 4

Cover with foil and bake for 30-35 minutes.

Step 5

Divide among serving plates and sprinkle with Parmesan cheese if desired. Serve immediately.