1 lb leanground beef, ground turkey, or ground chicken (or really, any ground meat or poultry will work well)
To make the spaghetti squash:
In the oven: Poke holes in the spaghetti squash and bake at 375 for 1 hour.
In the microwave: Cut spaghetti squash in half, put plastic wrap over the open side of the spaghetti squash and place, face-down, on a dinner plate that has about 1/4" of water in it, then microwave for about 10 minutes.
After cooking is done, remove the seeds and shred the spaghetti squash with a fork.
To make the casserole:
Cook turkey meat with your favorite spices.
Spray the bottom of baking pan then layer with spaghetti, meat, sauce, and 1 can of mushrooms. Bake at 350 for 30 minutes.