Using a double boiler technique: fill a medium size pot about halfway up with water and bring to a medium boil.
Fit a metal or glass bowl over top of the pan, then add all ingredients to the bowl, except the vanilla.
Using one hand, hold the bowl in place with an oven mitt. With your other hand, use your hand mixer to beat the mixture. Start on a low speed, and slowly increase to a high speed.
Continue to beat the mixture until it holds its shape—about 5-7 minutes.
Remove from heat and fold in vanilla extract.
Frost cupcakes or cake with an offset spatula or using a piping bag. Do not store in fridge or freezer.