Bring a large pot of salted water to a boil over high heat. Add the pasta and cook until tender but still firm to the bite, stirring occasionally, about 8 to 10 minutes.
In a medium bowl, stir together the bread crumbs, parsley, eggs, milk, ketchup, Romano cheese, and the salt and pepper. Add the chicken and gently stir to combine.
Using a melon baller (or a teaspoon measure), form the chicken mixture into 3/4-inch pieces. With damp hands, roll the chicken pieces into mini meatballs.
In a large (14-inch) skillet, heat the oil over medium-high heat. Working in batches, add the meatballs and cook without moving until brown on the bottom, about 2 minutes. Turn the meatballs over and brown the other side, about 2 minutes longer. Add the chicken stock and tomatoes. Bring to a boil. Using a wooden spoon, scrape up the brown bits that cling to the bottom of the pan. Reduce heat to low and simmer until tomatoes are soft and meatballs are cooked through, about 5 minutes. Drain the pasta, reserving about 1 cup of the pasta water. Transfer pasta to a large serving bowl and add the Parmesan. Toss to lightly coat orecchiette, adding reserved pasta water, if needed, to loosen the pasta. Add the meatball mixture, mozzarella cheese, and 1/2 cup of the basil. Gently toss to combine. Garnish with the chopped basil.