Preheat the oven to 400°F (200°C). Lightly spray or oil a large baking dish.
In a large bowl combine the ground beef, beaten egg, 1 tablespoon olive oil, Romano cheese, panko, 2 minced garlic cloves, dried basil, dried parsley, 1/2 teaspoon salt and 1/2 teaspoon pepper. Mix gently until just combined.
Using a teaspoon, form the mixture into small bite-sized meatballs and place them in the prepared baking dish in a single layer.
Bake the meatballs for 20 minutes, until cooked through.
While the meatballs bake, bring a large pot of salted water to a boil and cook the pasta shells according to package directions until al dente. Reserve 1/3 cup of the pasta cooking water, then drain the pasta.
Heat 1 tablespoon olive oil in a large skillet over medium heat. Add the remaining minced garlic and cook briefly until fragrant, about 30 seconds.
Add the diced tomatoes, chopped basil and the halved grape tomatoes to the skillet and simmer briefly to warm through, about 2–3 minutes. Stir in the reserved 1/3 cup pasta water.
Add the drained pasta to the skillet and toss to coat in the tomato mixture. Add the baked meatballs and gently fold to combine.
Turn off the heat, stir in the ciliegine (mini mozzarella). Serve topped with freshly grated Parmesan and additional basil leaves.
