Italian Baked Chicken and Pastina

From Giada De Laurentiis, Foodtv.com

1 cup pastina pasta or other small pasta                       

2 tablespoons olive oil
1/2 cup cubed chicken breast

1/4 cup diced onion 

1 clove garlic, minced

1 (14.5-ounce) can diced tomatoes with juice

1 cup shredded mozzarella            

½ teaspoon Italian seasoning                                   

Salt and pepper to taste

1 6-ounce can tomato sauce           
1/4 cup bread crumbs                                                

1/4 cup grated Parmesan
1 tablespoon butter, plus more for buttering the baking dish

Preheat the oven to 400 degrees F.

Cook pasta in boiling salted water until just tender, about 5 minutes. Drain pasta into a large mixing bowl.

Meanwhile, put the olive oil in a medium saute pan over medium heat. Add the chicken and cook for 3 minutes. Add the onions and garlic, stirring to combine, and cook until the onions are soft and the chicken is cooked through, about 5 minutes more. Put the chicken mixture into the bowl with the cooked pasta. Add the canned tomatoes, mozzarella cheese, and seasonings. Stir to combine. Add enough tomato sauce to make sure mixture will stay moist during cooking. Place the mixture in a buttered 8 by 8 by 2-inch baking dish. In a small bowl mix together the bread crumbs and the Parmesan cheese. Sprinkle over the top of the pasta mixture. Dot the top with small bits of butter. Bake until the top is golden brown, about 30 minutes.