PREHEAT the oven to 350˚F.
MELT the butter in a large pot over medium-high heat and add in the diced onions and mushrooms until lightly brown.
SPRINKLE the flour on top of the onions and mushrooms and mix in to form a roux and cook for 3 minutes.
POUR in the milk and whisk over low heat for 5-10 minutes until it becomes very thick.
WHISK in 1 cup of the shredded cheese until all of the lumps are melted.
ADD the sauce to a large bowl and mix it together with the drained tuna, frozen peas, cooked egg noodles and salt and pepper until completely combined.
TRANSFER the mixture into an ALCAN® Non-Stick Lasagna Pan and sprinkle on the remaining 1 cup of shredded cheese followed up by a sprinkling of the bread crumbs, completely covering the top.
PLACE ALCAN® Non-Stick Lasagna Pan on a non-disposable baking sheet for support. BAKE in the oven on 350˚F for 30-35 minutes or until the top begins to brown.