Preheat an oven to 325 F. In the bowl of a stand mixer, combine the egg whites (use fresh, not bottled), ¾ cup powdered sweetener, and 1 tsp vanilla extract. Whip on medium-high speed using a whip attachment until stiff peaks form.
Add in the unsweetened coconut flakes and ⅛ tsp kosher salt. Gently fold the coconut in until well blended.
Use a 1 oz cookie scoop to portion the cookies onto a silicone or parchment-lined baking sheet. You should be able to fit 12 on each sheet.
Bake for 11-12 mins a batch until the cookies are kissed with brown edges. Allow the cookies to cool completely before attempting to remove them. When removing the cookies, use a spatula to scrape them from the pan. Repeat with the remaining cookie dough.
Once the cookies are cooled, melt the chocolate in the microwave, leaving a few small solid pieces of chocolate in the mix. Stir to dissolve these small pieces. This method is a quick chocolate tempering technique that allows the chocolate to harden at room temperature.
Dip the very bottoms of each cookie into the chocolate. Sprinkle the edges with the crushed pistachios or roll the dipped macaroon in crushed pistachios. Place the cookies onto a clean parchment-lined baking sheet and allow the chocolate to harden. Keep the cookies stored in an airtight container for up to one week.