Preheat the oven to 375°F (190°C). Roll out the pizza dough and cut it into 12 squares.
Lightly grease a muffin tin. Press each pizza dough square into a muffin cup, pressing it against the sides to create a small cup shape.
Place one meatball in each cup. Spoon a bit of marinara sauce over each meatball, then sprinkle with mozzarella cheese and a little Parmesan. Finally, add a pinch of Italian seasoning on top. Use a pastry brush to apply a thin, even layer of egg wash on the surface of the dough
Bake the meatball cups in the preheated oven for 12-15 minutes, or until the crust is golden brown and the cheese is bubbly and melted.
Remove the meatball sub cups from the muffin tin and garnish with fresh basil if desired. Serve warm!