Mash sweet potatoes by putting through a sieve or beating in an electric beater or using a potato masher or food mill.
Add milk gradually (if you add it too fast it splashes and is hard to mix in).
Mix in remaining ingredients.
Put in buttered casserole.
Heat through (bake in slow oven (250 deg. F) for 20-30 minutes, or in microwave).
Cover top with marshmallows.
Return to oven until marshmallows are slightly melted and a bit brown (if the oven is too hot, the marshmallows will disappear!) This step can- not be done in the microwave.