1. Start oven, set at Moderate, 350° F. Rub a 2-quart baking dish with butter or margarine.
2. Brown the diced ham quickly in a frying pan.
3. Beat the egg into the diced sweet potatoes, add ham.
4. Rinse out the frying pan with the hot milk and add to the mixture. Add salt and nutmeg. Taste before you add the salt; the ham may provide enough salt.
5. Place the mixture in casserole. Bake 30 minutes.