Add 2 tablespoons of olive oil to a large skillet and set over medium high heat.
Season chicken with Italian seasoning and salt and pepper. Brown in skillet until cooked through, 4-5 minutes. Remove from skillet and set aside.
Add onions and cook until softened, 2-3 minutes. Add garlic and cook for 1 minute more.
Add marinara sauce, water, and pasta and stir until combined. Bring mixture to a boil.
Reduce heat to medium low, cover skillet, and cook until pasta is al dente, about 20 minutes. Lift lid and stir pasta every few minutes to make sure pasta isn't sticking.
Add chicken back to the skillet and stir until combined.
Top with mozzarella cheese and parmesan cheese. Combine breadcrumbs with remaining 1 tablespoon of olive oil and sprinkle on top of skillet.
Broil on high for 2-3 minutes until cheese is melted and breadcrumbs are toasted.
Notes
NOTES:
If you don't have a large skillet with a lid, a sheet pan works great in a pinch.
If needed, add more water a few tablespoons at a time to create a thick sauce when pasta is done. 2 cups was the perfect amount for me.