Preheat oven to 350 degrees F. Lightly spray a 2.5 quart (11 x 7-inch) baking dish.
In a large bowl, combine the soup, 1/4 cup melted butter,
sour cream, cheeses, onion, sausage (if using), salt & pepper. Mix well.
Fold in the potatoes, making sure they are well coated with the soup mixture.
Turn into prepared pan.
Mix the crushed crackers with the 1 tbs melted butter.
Top casserole with the buttered cracker crumbs.
Bake for 50-60 minutes, or until casserole is bubbly around the sides, the crumbs are golden brown and the potatoes are cooked in the center.
Serves 6-8 as a side or main dish