Preheat the oven to 375 degrees F and grease
a 2-quart baking dish.
In a large heavy-bottomed skillet, melt
1 tablespoon butter over medium-high heat. Saute the onions
until translucent and fragrant; season with salt and pepper. Add the mushrooms and cook, stirring occasionally for about 2 minutes. Stir in the sherry
and soy sauce and cook until the majority of the liquid has evaporated. Remove from the heat and set aside.
Melt the remaining 4 tablespoons of butter, in large heavy-bottomed saucepan over medium-low heat. Whisk
in the flour and cook for about 2 to 3 minutes. Slowly add the chicken broth
, whisking constantly. Bring to a boil, then whisk in the milk
. Reduce the heat to a simmer
and continue cooking for an additional 5 minutes.
Add the mushroom mixture to the white sauce
and stir in the lemon juice
. Season the sauce with salt and pepper, to taste. Add the drained tuna
and the peas; stir just to combine. Check seasoning and add more salt and pepper, if needed. Remove from heat.
Cook the egg noodles in a large pot of salted boiling water according to package directions just until al dente
and return it to the saucepan
. Add the sauce, stirring gently to coat the noodles. Transfer the mixture to the prepared baking dish.
In a mixing bowl, toss together the grated cheese
and the bread crumbs
with the 1 tablespoon of melted butter and toss. Sprinkle evenly over the casserole
. Bake until the topping is crisp
and the sauce is bubbling.