Not Your Mama'a Tuna Casserole

Why I Love This Recipe
My husband's mother took her tuna casserole recipe to the grave. So he described it to me and I did my best to approximate it. And then some. ;-)
The panko breadcrumbs absorb oil and moisture from the caseerole so the potato chip topping can stay crunchy.
Ingredients You'll Need
1/2 lb. wide egg noodles
1/4 cup butter
1/2 large onion, diced
1 rib celery, diced
1/2 cup sliced fresh mushrooms
3 tablespoons all-purpose flour
1 cup milk
juice of 1/2 lemon
1 teaspoon dried parsely
1/2 teasooon dried tarragon
salt & pepper to taste
1/4 cup grated parmesan cheese
1/2 cup grated cheddar cheese, divided into 1/4 cups
1/3 cup mayonnaise
1/3 cup sour cream
1 egg
3 green onions, sliced
1 cup frozen green peas
2 6-ounce cans chunk white tuna, drained
1/4 cup panko breadcrumbs
2/3 cup crushed ridged potato chips
Directions
Preheat oven to 450º F.
Grease a 9" x 13" casserole pan.
Bring 1 gallon of salted water to a boil.
Add egg noodles and cook until al dente, about 10 minutes. Drain.
Melt butter in a large pan over medium heat.
Add onion, celery and mushrooms and cook until onion is translucent.
Add flour to pan and stir constantly until flour just begins to brown.
Slowly add milk to pan, stirring constantly to make a thick sauce.
Add lemon juice, parsely, tarragon, salt & pepper.
Sir in parmesan and cheddar cheeses. Sir until cheese is melted.
Add mayonnaise and sour cream and stir to combine.
Remove pan from heat.
Add egg and beat quickly to combine before egg sets.
Stir in green onion, peas, tuna and cooked noodles.
Pour mixture into prepared casserole dish.
Top with, in order, panko bread crumbs, remaining cheese and crushed potato chips.
Bake for 20-25 minutes or until casserole is brown & bubbly.