Italian Buttercream

There are many different types of Buttercream. I have listed recipes for a few different types previously but my favorite is Italian Buttercream. It has a very light texture and consists of mostly butter and air. It will take food color but since the sugar to butter ratio is so low, it takes time for the colors to fully develop. You can also decorate (as flowers, shells, etc.) with Italian Buttercream but you have to keep a cool hand. Handling the decorating bag in a warm kitchen is especially tricky and this Buttercream is always ready to melt into little puddles in my hot mitts.
I have written variations of this recipe several times already but never have I posted the original, so here it is.

Italian Buttercream
adapted from The Whimsical Bakehouse

1/2 cup water
1 1/2 cups granulated sugar
3/4 cup egg whites (use only separated eggs or Eggology)
1 Pound plus 1/2 stick unsalted butter
Dash vanilla extract

In a small cooking pot, stir together water and sugar. Bring to a boil and using a pastry brush and water, wash down the sides of pan to remove any crystals. Do NOT stir again.

Boil 4 minutes then beat egg whites to stiff peaks.
With the mixer running, slowly pour the cooked syrup into the whites.
Beat at high speed until the bowl is cool to the touch (about 10 minutes).
Slowly add the butter and vanilla. Beat until light and fluffy.