Preheat oven to 350°F.
This recipe makes two 9-inch wide, thin discs. Use a bowl or cake pan to trace circles on the backside of your parchment paper and place them on the sheet pans.
Beat the egg whites in the bowl of stand mixer fitted with the whisk attachment until satiny peaks form, then begin adding in sugar a spoonful at a time and continue to whisk until stiff, shiny peaks form.
Add the cocoa powder, red wine vinegar and optional extract. Gently fold these ingredients into the meringue until the cocoa is well incorporated.
Use a piping bag or a spatula to create even rings of meringue on the parchment.
Place the pans in the oven and immediately reduce the heat to 300 degrees F. Bake for 40 to 45 minutes.
Allow to cool, then gently peel away the parchment.