Cook pasta until nearly done, according to pkg instructions. Drain, rinse, and set aside. In a large pot, heat butter over medium-high heat. Add garlic and saute for a couple of minutes. Add mushrooms and salt, then saute for a couple more minutes. Pour in 1 cup broth and cook several minutes, until liquid reduces by half. Sprinkle in flour, then stir mushrooms for another minute. Pour in remaining broth and stir, cooking for a few minutes until roux thickens. Reduce heat to medium low. Cut cream cheese into pieces and add to the pot. Stir to melt. Add turkey, olives, peas, bacon, and cheeses. Stir to combine, adding salt and pepper as needed.

Add cooked spaghetti and stir it to combine. Add more broth, up to 2 more cups broth, if needed for moisture while cooking. Pour mixture into a large baking dish and sprinkle top with crumbs. Bake 350F 20 minutes, or until the casserole is bubbly and crumbs are golden brown.