Cupcakes
3/4 cup butter, at room temperature
2 1/4 cups brown sugar
3 eggs
1 1/2 teaspoons vanilla extract
1 1/2 cups cooked, mashed sweet potatoes
3 cups all-purpose flour
1 tablespoon baking powder
1 1/2 teaspoons ground cinnamon
1 1/2 teaspoons ground ginger
3/4 teaspoon ground nutmeg
3/4 teaspoon baking soda
3/4 teaspoon salt
1/2 teaspoon ground cloves
3/4 cups milk
Marshmallow Frosting
4 egg whites, at room temperature
1 cup sugar
2/3 cup corn syrup
1 teaspoon vanilla extract