In a large saucepan, melt butter over medium to low heat. Add onions and ham and sautÚ for approximately 2 minutes.
Gradually add milk and cream, stirring until thick and bubbly. Do not boil.
Add sliced potatoes to cream mixture. Add salt and pepper to taste. Cover and simmer for 8 minutes.
Transfer mixture to a greased baking dish. Top with cheddar cheese (if using). Bake, uncovered, at 350F for approximately 45 minutes, or until
potatoes are tender.