Melt butter, set aside. In a large bowl, mix together pumpkin puree, eggs, milk, sugar, vanilla, cinnamon and nutmeg. Pour into baking dish.
Sprinkle dry cake mix evenly over the pumpkin mixture, covering completely. Pour melted butter on top to cover cake mix; do not mix or stir in. Butter should sit on top of cake mix.
Bake for 1 hour at 350 degrees. Let cool. Best served cold, topped with whipped topping, dash of cinnamon. Optional: garnish with mint.