I'll find any excuse to use the kitchen torch in my utensil drawer; it satisfies the inner pyromaniac in me. Not that I'm arbitrarily taking any old leftover and caramelizing a layer of sugar on top of it with stream of fire; sweet potatoes are perfectly complemented with a little added sweetness. If you don't already have a kitchen torch, I highly recommended getting one-or asking Santa to bring you one this year. Just don't burn the house down.
Preheat the oven to 400 degrees F. The leftover mashed sweet potatoes I'm using in this recipe already have butter and brown sugar in it, but even if yours doesn't, it won't really make a difference since you'll be adding sweet sugar on top. As for the creaminess, it won't hurt to add in the milk to the sweet potato mix either way. Mix them well in a bowl.
Fill 2 ramekins with the mixture; the amount will vary depending on what sizes you have. Then place the ramekins on a rimmed baking sheet and pour about a 1/2-inch layer of boiling water into the sheet to ensure even baking. Bake for 25 to 30 minutes.
Let the ramekins cool for about an hour. When they have, sprinkle a thin, but even layer of sugar on top of each. Then fire up your kitchen torch and caramelize the layer of sugar until it becomes a hard, sweet crust. Garnish with mint if you have some and want it to look extra fancy.