PREHEAT the oven 350˚F.
MELT the butter in a large pot on high heat and add in the onions to sauté, about 4 minutes.
WHISK in the flour to form a roux.
POUR in the milk and cook over medium heat until it becomes thick.
WHISK in 8 ounces of shredded mozzarella cheese until it is completely combined.
ADD the cooked noodles, chopped cooked chicken, chopped tomatoes and basil to the pot with the sauce and mix until combined. Season with salt and pepper.
POUR the mixture into an ALCAN® Non-Stick Lasagna Pan and sprinkle on the remaining 1 cup of shredded mozzarella cheese.
PLACE ALCAN® Non-Stick Lasagna Pan on a non-disposable baking sheet for support. BAKE in the oven for 30 minutes or until the cheese on top is lightly browned.
GARNISH with chopped tomatoes and basil.