Preheat your oven to 200 degrees; set your oven racks into the bottom half of your oven (ready to accommodate two cookie sheets).
Line two cookie sheets with parchment paper and set aside.
Using a stand mixer, begin whipping the egg whites (on a high speed) in a clean and dry mixing bowl. Once they have started to get foamy, add the cream of tarter and vanilla (or flavored creamer). Continue whipping until the eggs became a soft meringue.
Begin adding the ground sugar into the mixture, a tablespoon at a time so it can dissolve into the meringue. Once all the sugar is in the meringue, allow it all to whip at high speed until the meringue is stiff and glossy.
Turn off the mixer and stir in the cocoa, instant coffee, and (if desired) ground cinnamon until completely mixed in and of even color.
Fill a piping bag (pre-fixed with your desired medium-large tip) or a large ziplock bag with the meringue. If using a ziplock bag (which is what I do), put the meringue in so that it fills a bottom corner of the bag and then cut off the corner so that the meringue can be "piped" out.
Pipe out the meringues -- roughly 1.5 or 2 inch circles. You can fit them closely together because they will not spread as they bake.
When both pans are filled, place them in the oven and let back roughly 90 minutes or until they are dry, firm to the tough, and able to be lifted easily off the parchment paper.
Turn off the heat and use a wooden spoon to crack open the oven door. Allow the meringues to remain in the oven at least 2 hours (or overnight) so they can completely dry.
Once they have finished drying, remove them from the parchment paper and store in an air-tight container for up to 2-3 days.
Or ... you know ... eat them all right away.
Notes
*You can use "Superfine" sugar or make your own by putting the 1 cup of granulated sugar in a blender and blending it for 30-60 seconds.
**I prefer a dark roast when making these so the coffee flavor really comes through; the Starbucks Via packets are exactly 1 teaspoon each.
Recipe by Following In My Shoes at https://followinginmyshoes.com/my-recipes/double-espresso-mocha-meringue-cookies/