Preheat the oven to 350 degrees F (175 degrees C). In a medium bowl, mix together the ricotta cheese, mascarpone cheese, sun-dried tomatoes, bread crumbs, oregano, salt and pepper until well blended. Set aside.
Bring a large pot of lightly salted water to a boil. Trim the ends of the squid bodies to make them an even size, and rinse out the tubes. Spoon the cheese mixture into the cavities of the squid until full, and secure the open ends with toothpicks. Place in boiling water, and cook for 6 minutes.
Remove the stuffed calamari tubes from the water, and place in a baking dish. Bake for 20 minutes in the preheated oven.
Melt butter in a large skillet over medium heat. Add garlic and sesame seeds. Place the calamari tubes in the skillet, and fry on all sides until golden brown. Remove toothpicks before serving.