Instructions

1. Fill a medium saucepan about 1/2 full with water.  Bring it to a boil over medium heat and reduce the heat to medium-low so that it just simmering around the edges, not boiling.
2. Add the egg whites, sugar, water, and cream of tartar to a large heatproof bowl of a stand mixer.  If you don’t have a stand mixer, just make sure you use a heatproof bowl.
3. Place the bowl over the saucepan of simmering water.  Whisk the mixture frequently, for about 5 minutes, until the sugar has completely dissolved and it will also be foamy.  This takes about 5 minutes.  Check it by rubbing a tiny bit of the mixture between two fingers.  If it feels grainy, the sugar has not dissolved yet.
4. Place the bowl on the stand mixer fitted with the whisk attachment.  Beat on high speed until the frosting is very glossy and triples in volume, about 7 minutes.  Mix in the vanilla and any food coloring, if using.
5.  Spread the frosting on a cake or cupcakes as desired.
6. This frosting will hold up for 4 to 5 days at room temperature.