Preheat oven to 350 degrees F.In a stock pot, boil one gallon of water. Add sliced potatoes and cook for 10 minutes. Drain.In a sauce pan, whisk together heavy whipping cream, butter, and cream cheese until smooth. Remove the cream mixture from heat.In a large bowl, stir together cream mixture, sour cream, cottage cheese, salt, pepper, and ¾-pound sharp Cheddar, with a spatula.In a food processor, pulse Ritz crackers and remaining sharp Cheddar and queso chihuahua cheese until a fine crumb.Layer mixture with potatoes in a 9-by-13 casserole dish and top with cracker/cheese crumbs. Bake for 90 minutes, until bubbly.