1. Place potatoes in a large pan or stock pot and cover with cold water, so the water is at least 1″ above the potatoes. Heat on medium high until boiling. Reduce heat to medium (or as low as you need to go so potatoes are still boiling but not over!) and continue to boil until potatoes are tender. Drain and return to pan. 2. Preheat oven to 350 and grease a baking or casserole dish. Mash potatoes. Add butter and mix well. Stir in onion, ham, sour cream, half and half and 1 cup of cheese. Add salt and pepper and mix well. 3. Pour into prepared baking dish and top with remaining cheese. 4. Bake for 20-25 minutes or until center is hot.