Whisk the egg whites: Whisk the egg whites in a clean bowl until they begin to foam, about 1 minute. Slowly add in the granulated sugar and continue whipping until stiff peaks form. The mixture should be thick and glossy—when you lift the whisk, the meringue should form stiff peaks.
Add the sifted confectioners' sugar, almond meal, and espresso powder into the meringue. Using a spatula, fold the dry ingredients into the meringue until it is fully incorporated. The batter should have a consistency similar to molten lava. To test, scoop up a spoonful of batter and drop it back into the bowl; it should flatten and sink into the batter within 15 seconds. If it doesn’t, keep folding it.
Transfer the batter to a piping bag fitted with a large round tip. Pipe small rounds (about 1.5–2 inches in diameter) onto a baking sheet lined with parchment paper or a silicone mat, using a template to ensure uniform sizes. Leave at least ½ inch of space between each round.
Gently tap the bottom of the baking sheet against the counter to release any air bubbles. Let the macarons sit out for 30 minutes, or until the tops have dried and form a skin (the batter shouldn't stick to your finger when you touch it).
Preheat your oven to 300°F. Bake the macaron shells for 10-12 minutes, or until they have firmed up and no longer feel sticky when touched. Let them cool completely on the baking sheets before removing.