Heat olive oil in a large skillet with a right fitting lid (use an oven safe or cast iron if you've got one) over medium heat. Add the onion and cook until translucent, 3-4 minutes. Add the garlic and cook a minute or so more, until fragrant.
Add the chicken to the skillet and season with salt and pepper. Cook, stirring frequently, until browned, about 5 or so minutes.
Increase the heat to med-high. Add the tomato sauce, diced tomatoes, broth, milk and sugar to the skillet. Season to taste and bring to a boil.
Once at a boil, stir in the pasta and reduce heat back down. Cover with the lid and let simmer for 13-15 minutes, stirring occasionally, until the pasta is al dente and the sauce is reduced a bit.
While the pasta is cooking, melt the butter in a small bowl and stir it into the breadcrumbs and the additional tsp. of Italian seasoning. Set aside until pasta is done. Preheat the oven to 350F. If not using an oven safe skillet, then grease a large casserole dish and set it aside.
If using an oven safe skillet : sprinkle both of the shredded cheeses over the top of the pasta and then top with the breadcrumbs. Bake in the oven for 10 minutes. Then turn the oven to broil for an additional 2-3 minutes, until the top is golden brown (watch carefully at this point, so your toppings don't burn!).
If NOT using an oven safe skillet : pour your chicken and pasta mix into the prepared casserole pan. Sprinkle with both cheeses and top with the breadcrumbs. Bake in the oven for 10 minutes, then turn the oven to broil for an additional 2-3 minutes (watch carefully at this point so your toppings don't burn!).
Serve immediately and enjoy! Refrigerate any leftovers.
