Heat proof bowl that would fit on a saucepan to use as a double boiler.
In the saucepan, bring two inches of water to a low simmer.
In a clean heat safe bowl, place the egg whites and sugar and mix them well with a whisk.
Place this bowl on top of the saucepan with barely simmering water and mix continuously. This is important as whisking prevents the egg whites from cooking and curdling. You are not looking to incorporate air here, but just to keep the mixture moving.
Stir the egg white and sugar with the whisk for about 2-3 minutes until the sugar dissolves and the egg whites become creamy white in colour. If you have a food thermometer - heat the egg whites while whisking to 145°-150°F/ 63°-66°C. If the sugar dissolves, you have heated the eggs to this temperature.
Remove the eggs from the double boiler and immediately start whisking the egg whites with a hand mixer, to make the meringue.
Whisk on high for about 3-4 minutes until the egg whites have tripled in volume and has stiff peaks.
Add vanilla and mix for a few seconds till it's well incorporated..
Store in an airtight container until ready to serve.