To prepare the macarons:

1. Line two of three baking sheets with parchment paper templates or silicone baking mats set over the templates and fit a large piping bag with a plain round tip.
2. In a food processor, combine the almond flour, confectioner’s sugar, cocoa powder, and instant coffee and process the mixture for 1-2 minutes, stopping once to scrape down the bowl, until the almond flour is finely ground. Sift the mixture through a fine-mesh sieve into a large bowl. Discard any large chunks left in the sieve or grind again until fine.
3. In the bowl of a stand mixer fitter with a whisk attachment (make sure both are clean and grease-free!), whisk the room temperature egg whites and cream of tartar on low speed until they begin to foam, form small tight bubbles, and turn opaque. Over the course of a couple of minutes, very gradually increase the speed to medium while slowly adding the granulated sugar. Mix on medium-high until stiff peaks form.
4. Using a flexible rubber spatula, scrape the meringue off the whisk attachment into the bowl with the almond mixture. Begin folding the meringue and almond mixture together, five to ten folds. Scrape in the meringue from the mixer bowl and continue to fold the mixture until incorporated, rotating the bowl as your go. Every so often, gently deflate the meringue by smearing the batter around the side of the bowl. Stop folding once the correct consistency is achieved: the batter should flow very slowly like lava.
5. Fill the prepared piping bag with the macaron batter. Holding the bag straight down, pipe the macarons. I prefer to use a stencil to ensure the macarons are the same size. Once one baking sheet is full, tap the bottom of the sheet a few times in each corner with the palm of your hang. Set aside and repeat with the remaining prepared baking sheet(s). Set the piped macaron shells aside to rest for 20 to 40 minutes, until a skin forms over the shells and the tops feel dry and not tacky to the touch.
6. Preheat the oven to 325 degrees with a rack in the center position.
7. Bake the macaron shells once sheet at a time for 12 to 14 minutes, until the tops feel secured to the feet but wiggle very slightly when nudged.
8. Remove the baking sheet from the oven and place it on a wire rack. Let the macaron shells cool on the baking sheets for at least 5 minutes. Repeat to bake and cool the remaining shells.

To prepare and use the filling:

1. Cream the butter using a mixer on medium speed until smooth, about 1-2 minutes. Add the powdered sugar, cocoa powder, and extract and stir on low to combine. Add water a teaspoon at a time until the buttercream comes to the preferred consistency. It should be soft and spreadable but not runny.
2. Fit a piping bag with a round tip and squeeze 1-2 teaspoon sized dollops into the center of half of the macaron shells.
3. Top with an additional macaron shell and allow to set up. In the meantime, feel free to gently warm and melt a small about (about 1/3 cup) of chocolate and drizzle or piping decorative stripes on top of the sandwich cookies. Sprinkle on the crushed peppermints and place in the fridge to set up. Enjoy!