Preheat oven to 325 degrees F. Grease a 1-quart casserole.

In a saucepan, scald 3 cups milk, then add molasses and cornmeal, and cook until thick. Remove from heat.

In a bowl, blend together egg, sugar, salt, ginger, and cinnamon. Add to warm milk mixture. Pour into prepared casserole and bake for 30 minutes. Add ½ cup cold milk and butter. Continue baking for about 1 hour.