Swiss meringue

Separate the eggs while cold, keeping out all yolk.

Add the cream of tartar and the sugar to the whites in a heat-safe mixer bowl.

Set the bowl over a pot of barely simmering water without the bowl touching the water.

Whisk constantly until the sugar dissolves and the mixture reaches 160F, so the eggs are safe to eat and do not scramble at the edges.

Return the bowl to the stand mixer, whip on low, then raise gradually to medium high and whip to the desired peaks.

Spread onto a finished baked good such as a pie, kept to medium peaks and swooped.