Start by sifting the almond flour to remove any lumps, then sift together with the powdered sugar thoroughly and set this mixture aside.
Pour granulated sugar into a separate container, ensuring all your utensils and bowls are completely dry and grease free for the best meringue.
In a clean bowl, whip the room temperature egg whites on low speed until they froth; add the cream of tartar, then slowly add granulated sugar in three parts while gradually increasing speed until glossy, stiff peaks are formed.
Fold one third of the almond flour and powdered sugar mix gently into the meringue using a folding 'J' technique, then incorporate the rest carefully to deflate the batter slightly; check that the batter flows smoothly off the spatula forming a ribbon and a figure-eight shape.
Gently fold in the espresso powder a few times until the batter is evenly flavored.
Transfer batter into a piping bag fitted with a 1/4 inch round tip and pipe one-inch rounds onto parchment or silicone mats on baking sheets; tap the trays firmly on the counter to remove air bubbles, then pop any visible air bubbles with a toothpick.
Allow the macarons to rest at room temperature for 30 to 60 minutes until a dry skin forms and the surface is matte and not sticky.
Preheat the oven to 325°F (use an oven thermometer for accuracy) and bake the macarons individually for 11 to 14 minutes until they are firm and set without any wobble.
Remove the macarons from the oven and cool them completely on the tray before carefully peeling them off.
Prepare the buttercream by beating together softened cream cheese and butter until smooth and fluffy, then mix in powdered sugar, espresso powder, vanilla extract, salt, and Nutella or cocoa powder until fully blended; adjust consistency with milk if needed.
Fill a piping bag fitted with an open star tip with the buttercream and pipe decorative swirls or stars onto the shells, sandwiching them together.
Melt the chopped semisweet chocolate and put it in a small piping bag with a tiny hole, then drizzle artfully over the filled macarons.
For best flavor, refrigerate the assembled macarons overnight to allow the filling and shells to harmonize. Enjoy at your convenience!
