Swiss Meringe Buttercream

3 1/3 sticks of butter
4 egg whites
1/3 lb butter
3 tsp vanilla

Put eggs and sugar in mixer bowl and set that over a pan of simmering water. ( The water should not touch the bottom of the mixer bowl). Using a whisk and a thermometer, whisk the eggs until they reach 110*. Place mixer bowl in mixer and whip egg whites on high until they form stiff peaks, about 8 min. Reduce speed and add vanilla and whip. Add butter one tablespoon at a time and whip until light and fluffy.