Preheat oven to 350 degrees Fahrenheit. Line a 12-cup cupcake tin with paper liners.
Add the egg whites, water, vanilla extract and cream of tartar to the bowl of a stand mixer fitted with the whisk attachment. Start beating the egg whites on medium speed. After 1 minute, slowly pour in the sugar. Continue beating the egg whites until medium peaks can be held. This means that if the whisk is lifted out of the eggs, a peak will form but with a tip that may not stand up straight. It took approximately 6 minutes in my stand mixer on medium speed.
Sift the dry ingredients; flour, cornstarch and cocoa powder, over the egg whites 1/3 at a time. Fold in each third gently before adding more, being careful not to deflate the egg whites.
Fill the cupcake liners 3/4 full. Bake for 14 to 16 minutes or until a toothpick inserted in the middle of the cupcake comes out clean. Allow to cool in the pan for 5 minutes, then transfer to a cooling rack.
Again in the clean bowl of a stand mixer fitted with the whisk attachment, place the heavy cream, sugar and vanilla. Whip on medium speed until it can hold a nice peak when the beater is lifted, approximately 5 minutes. Be careful not to whip too long or the whipped cream will turn to butter!
Place the whipped cream into a piping bag fitted with any large tip, I used 1M. Pipe the topping on to your cupcakes. Top each one with a cherry (or berry of choice), and store in the refrigerator until serving.
I used Hershey's Special Dark cocoa. Any cocoa can be used, but the cupcakes may be lighter in color and chocolate flavor depending on the brand.These can be made with a handheld mixer! Or even a whisk! It will take longer to reach the proper thickness for both the egg whites and the whipping cream.The calories shown are based on the recipe making 12 cupcakes, with 1 serving being 1 cupcake. Since different brands of ingredients have different nutritional information, the calories shown are just an estimate. **We are not dietitians and recommend you seek a nutritionist for exact nutritional information.**