Chicken Noodle Casserole

This is one that has been requested to post. It's a good one!

Note: the recipe calls for egg noodles. You can certainly purchase them, I like to make my own - which are simple but take a little more time (maybe 15-20 minutes). I use the recipe for egg noodles out of the Betty Crocker cookbook, and mix it on the Kitchenaid.

Topping:
2 Tbsp. unsalted butter, melted
1 cup fresh bread crumbs
1/2 cup grated Parmesan cheese
1 Tbsp. chopped fresh Parsley

Filling:
Salt
12 oz. egg noodles
6 Tbsp. unsalted butter
1/2 small onion, chopped fine
1 lb. white mushrooms, cleaned and sliced thin
Pepper
1/4 c. all-purpose flour
2 garlic cloves, minced
3 cups chicken broth
2 cups sour cream
4 cups cubed chicken
1 Tbsp. chopped fresh parsley
2 tsp. chopped fresh thyme
1/4 tsp. nutmeg

For the topping: Mix melted butter, bread crumbs, Parmesan, and parsley together in a bowl.

For the filling: Adjust oven rack to middle position and heat oven to 350 degrees. Bring 4 quarts water to boil in a large pot. Add 1 Tbsp. salt and noodles, and cook until nearly tender. Drain and set aside in colander.

Melt 2 Tbsp. butter over medium heat in your now-empty, large pot. Add onion and cook until lightly browned, about 5 minutes. Add mushrooms, 1/2 tsp salt, and 1/4 tsp. pepper, and cook until mushrooms begin to brown, about 7 minutes.

Stir in remaining 4 Tbsp. butter until melted. Add flour and stir until lightly browned, about 2 minutes. Add garlic and cook until fragrant, about 30 seconds. Gradually whisk in broth and sour cream, and cook - not letting mixture boil, until thickened, 5-7 minutes. Stir in chicken, noodles, parsley, thyme, and nutmeg and season with salt and pepper.

Transfer mixture to a 3 quart baking dish. Top with bread-crumb mixture and bake until browned and bubbly, about 30 minutes. Cool 5 minutes. Serve.