Grease or oil a 3 quart shallow baking dish. Set it aside for now.
Cook your egg noodles according to package directions.
While the noodles are cooking, melt 2 Tablespoons of the butter in a small saucepan over medium heat.
Whisk in the flour and let it cook for 1 minute.
Add in the milk, salt, pepper, and onion powder (optional). Stir and cook until the milk mixture begins to boil and thickens. Remove it from the heat.
Stir in all but about 1/3 cup of the cheddar cheese, mixing until it is melted.
In a mixing bowl, combine the sauce, noodles, cooked chicken, and peas.
Note: We like the peas just cooked with still a little crunch. If you want the peas cooked softer, add them to the noodles in the last few minutes while they are cooking.
Spread the mixture into your prepared baking dish. Sprinkle with the remaining cheese.
Melt the remaining tablespoon of butter and combine it with the bread crumbs. (See the note below.) Sprinkle the buttered crumbs over the top of the casserole.
Bake covered for 15 minutes. Uncover and bake for 10 more minutes.
Enjoy!
Video
Notes
I make my own bread crumbs by toasting a couple pieces of bread. Let them cool and pulse in a food processor.