On high speed in a stand mixer (or with a hand mixer), beat vanilla and egg whites until frothy and bubbly.
A little bit at a time, add in the powdered sugar until the sugar is dissolved. To keep the mess down, add a bit of sugar with the mixer on low and beat it just until it pulls it into the egg whites, turn the mixer up and mix it until incorporated. Repeat
When the sugar is incorporated, turn the mixer on high and beat until stiff peaks form. This takes about 8 minutes in a stand mixer and about 11 minutes with a hand mixer. You are looking for a mountain that doesn't curl. Or, if you flip the beater upside down the egg white doesn't flop over AT ALL.
Use immediately or store in air-tight containers.
You can dye this with food coloring.
Adjust the consistency to what you desire for your icing needs.