Prepare the double boiler - Fill a large pot 1/3 the way with water and bring to a gentle boil. Place a heat proof bowl on top making sure the bottom of the bowl isn’t touching the water. Turn the heat down to low medium.
Whisk egg whites and sugar - Add the egg whites, caster sugar, cream of tartar and vanilla extract to the bowl. Gently whisk your egg white and sugar mixture for about 3–4 minutes on medium high speed, or until the sugar is completely dissolved and you reach 72C / 160F on a candy thermometer.
How to check your meringue is ready to whip - run some of the mixture between two fingers. If you can’t feel the sugar granules, then it’s time to take it off the heat.
Whip meringue - Use an electric hand mixer or stand mixer fitted with a whisk attachment to whip for 4–5 minutes until thick and glossy. It's ready to use!
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Notes
This meringue needs to be made fresh and used fresh. There's no making this frosting ahead of time to store it in advance. Having said that, this meringue can sit on top of a tart for about 6 hours before it begins to melt. I’ve even had it on top of my Lemon Meringue Pie in the fridge overnight with some weeping (melted sugar).Nutrition - is based on this recipe being used to frost 12 portions of dessert. Like 12 cupcakes for example.Egg whites - The egg whites in this recipe are gently cooked which makes them safe to eat. However, like all recipes that use eggs in this manner, they are not safe for pregnant people. I also recommend using fresh eggs for this recipe and not carton egg whites.Caster Sugar - Caster sugar is a finer version of regular granulated sugar. It is often used for meringues because it dissolves quicker which means there’s less chance of overwhipping the meringue. Can you use granulated sugar instead? Yeah, you can. Just be careful not to overwhip the frosting. What does overwhipped frosting look like? It looks like little bits of scrambled egg in your frosting that melts within hours of being used.A note on measurements - this recipe is offered in weight measurements. This is in an effort to offer the most accurate way to get the best results. Cup measurements simply aren’t accurate enough for a recipe that needs precision and cup sizes differ depending on where you are in the world. Here is where you can learn more about how to measure ingredients using digital kitchen scales!