Preheat oven to 350. Prepare casserole. Slice potatoes width wise to make very thin circles. Slice the onion thinly. Layer potatoes, onion, cheddar, and dash of spices repeating until dish is 3/4 full. Top with cheddar. Pour milk into casserole to about half way up the sides. Bake for 1 1/2 hours until potatoes are tender.