Prepare the squid by cleaning under cold water, removing innards and the beak. Separate into tubes and tentacles, dicing tentacles into small pieces. Pat squid tubes dry.

Cook the sausage in a large, oven-safe skillet over medium heat until browned for about 5 minutes. Add minced garlic and red pepper flakes for another minute.

Combine the cooked sausage mixture in a food processor with diced tentacles, breadcrumbs, Parmesan cheese, parsley, salt, and black pepper. Pulse until well combined.

Stuff each squid tube with the filling, leaving a small space at the end to prevent spilling. Pinch the open ends to seal.

Sear the stuffed calamari in the same skillet with olive oil for 1-2 minutes on each side until lightly browned.

Preheat your oven to 350°F (175°C). Pour sauce over the calamari and bake uncovered for 15-20 minutes until bubbling.

Garnish with extra parsley and serve hot, accompanied by pasta or salad.