Preheat the oven to 380°F (193°C). Line a baking sheet with parchment paper and generously grease a standard 12-cup metal muffin tin, including around the openings.
Combine the ground turkey, breadcrumbs, egg, Parmesan, garlic, Italian seasoning, salt, and pepper in a bowl. Mix gently until just combined, then divide into 12 equal portions.
Flatten each portion of turkey mixture and place a cube of mozzarella in the centre. Wrap the meat around the cheese and roll gently into a ball, sealing completely so no cheese is exposed. Arrange on the prepared baking sheet.
Bake for about 16 minutes, or until the turkey reaches 165°F (74°C). Check the temperature in the meat beside the cheese centre. Let cool slightly, leaving any released liquid on the baking sheet. Increase the oven temperature to 400°F (200°C).
Roll out the pizza dough into a 16"x12" rectangle and cut out 12 x 4-inch squares. Press the squares into a greased muffin tin, leaving the corners overhanging.
Add one cooked meatball in each dough-lined cup, then top with 2 teaspoon marinara and 2 teaspoon shredded mozzarella.
Bring the overhanging dough over the filling and pinch firmly to seal, gently spreading thick folds of dough so the tops bake evenly. Keep each muffin contained within its own cup.
Bake for 10-12 minutes, until golden brown and the dough is cooked through around the sides and bottom.
Stir together the melted butter, garlic powder, and Italian seasoning. Brush over the muffins and sprinkle with the Parmesan as soon as they come out of the oven.
Let rest in the tin for 5 minutes, then carefully remove. Serve warm with extra marinara for dipping.