Vanilla Cupcakes with Marshmallow Frosting

Ingredients 

For the Cupcakes

1/2 c. butter
1/2 c. water
3/4 c. sugar
1 egg
1/4 c. sour cream
1 t. vanilla
1 c. flour
1/4 t. salt
1/4 t. baking soda

Frosting

2 egg whites
1/4 t. cream of tartar
1/2 c. sugar
1/2 t. vanilla

Instructions

1. Boil butter and water. Add sugar. Stir until dissolved. Let cool. Add egg, sour cream, and vanilla. Stir. Add flour, salt, and baking soda. Stir until combined. Pour into lined muffin tins (I use these) and bake at 350 for 18 minutes or until toothpick comes out with tiny crumbles on it.

2. In a double boiler (or using a heatproof bowl set over a pan of simmering water – what I do is put a small pan inside of a larger one half-filled with boiling water) combine the egg whites, sugar, and cream of tartar. Whisk the mixture frequently until it is very frothy and measures approximately 160 degrees (I use an infrared thermometer like this one to measure the temperature). Carefully add the egg whites to the bowl of a stand mixer fitted with the whisk attachment. Whisk on high speed until the egg mixture holds stiff peaks and is a light texture (several minutes). Carefully fold the vanilla into the egg whites mixture. Frost cupcakes and enjoy!