1. Preheat the oven to 200°F (93°C) (If you have two ovens, turn one onto 200°F and the other onto 375°F). Combine the confectioners’ sugar and almond flour in a medium bowl. If grinding your own nuts, combine nuts and a cup of confectioners’ sugar in the bowl of a food processor and grind until nuts are very fine and powdery. If your almond flour is a bit wet, put it into the 200°F oven for about 10 minutes or until it’s dry.
2. Beat the egg whites in the clean dry bowl of a stand mixer until they hold soft peaks. Slowly add the granulated sugar and beat until the mixture holds stiff peaks. It will be shiny and about quadrupled in size.
3. Sift a third of the almond flour mixture into the meringue and fold gently to combine. If you are planning on adding zest or other flavorings to the batter, now is the time. Sift in the remaining almond flour in two batches. Be gentle! Don’t overfold, but fully incorporate your ingredients.
4. Spoon the mixture into a pastry bag fitted with a plain half-inch tip (Ateco #806). You can also use a Ziploc bag with a corner cut off. It’s easiest to fill your bag if you stand it up in a tall glass and fold the top down before spooning in the batter.
5. Pipe one-inch-sized (2.5 cm) mounds of batter onto baking sheets lined with nonstick liners (or parchment paper). Leave sitting on the counter for at least an hour.
6. Bake the macaroon for 5 minutes in the 200°F oven. Remove the pan from the oven and raise the temperature to 375°F (190°C) (or move the pan right into the other oven that’s already at 375°F). Once the oven is up to temperature, put the pans back in the oven and bake for an additional 7 to 8 minutes, or lightly colored.
7. Cool on a rack before filling.

For the french chocolate buttercream

1. Add water and sugar to a small saucepan, place on med-high heat until 115 degrees Celsius. Do not stir once it begins to boil. While the sugar syrup is boiling, begin to whip the eggs yolks on med speed until they are light in color and have thickened considerably (they should vaguely resemble a custard). Very CAREFULLY and SLOWLY pour the sugar syrup into the egg yolks while the mixer is still going (have a friend do it, if you’re using hand mixer). You don’t want to scramble the eggs or crystallize the sugar. Continue on medium speed until no longer hot (feel side of the bowl, it should be about body temperature). Slowly add the butter in chunks, allowing it the be incorporated fully before adding more. Once all the butter has been added, add the vanilla, cocoa powder and melted chocolate. Add more cocoa powder to taste. It will be runny, but will thicken once refrigerated. Once thickened, fill the macaroon with a pastry bag.