This recipe uses a ratio of egg whites to granulated sugar so you can always use up leftover egg whites you may have. 1:2.

Make sure your utensils and bowl are scrupulously clean before starting and assure your eggs are at room temperature. A little soak in a cup full of warm tap water before separating them can do the trick.

Mocha Meringue Cookie 

4 egg whites, room temperature, weigh

2 x the weight of the eggs for the granulated sugar

1/4 teaspoon kosher salt

1/4 teaspoon cream of tartar

1 teaspoon vanilla

2 teaspoons espresso powder

2 Tablespoons cocoa 

Preheat oven 225 degrees, no fan. 

Weigh egg whites, and put into the bowl of the stand mixer. Take the weight and double it to get the weight of granulated sugar. 

Add the salt and cream of tartar to the egg whites. Whip until just foamy then add the sugar a tablespoon at a time, over 4 to 5 minutes. Whip until you can not feel the granulated sugar when you rub it between your thumb and forefinger. 

Add the vanilla.

Sift the espresso powder and cocoa before adding it to the egg mixture.  Whip into the egg white mixture. 

Fit a piping bag with a decorative tip. Fill with meringue and pipe kisses, roses or discs or swirls. Bake for 1 full hour. The cookies are done when you can pick on up off the tray and they are completely dry.