In a large bowl combine sour cream, cream of chicken soup, french onion soup package, salt and pepper (to taste) and 2 cups of cheddar (the rest is for topping) and optional onion and mix well. After the sauce is mixed thoroughly add shredded potatoes. Fold the potatoes in using your hands to mix. A spoon can be used, however is very difficult. I recommend using vinyl or rubber gloves as the potatoes are very cold! Lightly coat a 9x13 baking dish with non stick spray and press 2/3 of the potato mix in to the bottom. Make sure the mixture is even in thickness, evenly distribute sausage to the top of potato mix. Add the rest of the potato mix to the top of the sausage, and cover the entire casserole with remaining cheese. Cover with foil and bake for 45 minute Remove foil and bake for an additional 10-15 minutes or until cheese is bubbly. Let sit for about 10-15 minutes -- It will be lava hot! Enjoy!