I first whipped up this casserole because I had a chicken in the fridge, a couple of boxes of mushrooms and the sheer will to eat a big ol' plate of comfort food. It resembles a tetrazzini more than anything, but is a little more on the simple, pared-down side. No onions, no celery, no carrots. Just creamy, mushroom-y loveliness.
Place chicken in a pot of water and boil on medium-low heat for 30-40 minutes. Remove chicken from pot and allow to cool slightly. Keep broth in pot.2.
Melt 2 tablespoons butter in a large skillet. Throw in mushrooms, add 1/4 cup white wine, and sprinkle with salt and pepper. Cook over medium heat for 8-10 minutes, or until liquid has totally evaporated. Remove mushrooms from skillet. Set aside.3.
Bring broth to a boil. Break spaghetti into thirds (shorter pieces). Add spaghetti pieces to boiling broth and cook. Drain when al dente. Remove meat from bones and shred until you have 2-plus cups of shredded chicken.4.
Return large skillet to medium-low heat. Add 6 tablespoons butter. Sprinkle flour over butter, whisking to combine. Cook for 1-2 minutes. Pour in 2 cups broth and whisk to combine. Pour in milk, additional 1/4 cup wine, salt and pepper to taste, then cook and bubble until thick. Turn off heat, add Parmesan cheese, and stir.5.
Add mushrooms, chicken, and chopped olives. Stir to combine and check seasonings. Add cooked spaghetti and stir.6.
Turn into a 9- by 13-inch casserole pan. Bake at 350°F or until golden brown and bubbly. Serve with salad and warm, crusty bread.