Preheat the oven to 350 degrees F.
Add the butter, mushrooms, onion, and garlic in a large skillet. Sautee the vegetables until they are tender about 5 to 7 minutes.
Add the 1/4 cup of flour and stir in until it is mxed in well
Increase the heat to medium-high and gradually add milk and broth stirring constantly. Bring to a boil and reduce heat to medium-low and continue to cook for about 7 to 8 minutes. The sauce should reduce slightly and thicken. Season with salt and pepper if desired.
Remove from the heat once the sauce is thickened add the tuna, egg noodles, and peas.
Pour into a 1 1/2 to 2-quart casserole dish, sprinkle the crushed potato chips over the top of the casserole and place it into the preheated oven.
Bake for 25 to 30 minutes or until the topping is lightly browned and the sauce is bubbly.