Squash Casserole

3 pounds mixed yellow and zucchini squash
1 onion, sliced
3 tbsp. unsalted butter
3 eggs, beaten
1 10 3/4 oz can cream of mushroom soup
3/4 tsp. salt
1/2 tsp. pepper
cracker  crumbs 
Parmesan cheese

Cook the squash and onion in a little water (this can be in the microwave if you want)
until tender. Drain and mash. fold in butter, beaten eggs, soup and salt and pepper. Place
in a buttered casserole dish and top with the cracker crumbs and sprinkle with cheese.
Bake at 350 for 30 minutes.