Prepare the Macaron Shells:
Preheat your oven to 300°F. Sift together powdered sugar, almond flour, and hazelnut coffee grounds.
Whisk Egg Whites:
Whisk egg whites in a clean bowl until stiff peaks form. Gradually add granulated sugar, continue whisking.
Mix Wet and Dry Ingredients:
Fold the sifted ingredients into the meringue gently, making sure to maintain the airiness.
Pipe the Macarons:
Transfer the batter to a piping bag and pipe small circles onto a lined baking sheet. Tap the tray to remove air bubbles.
Bake:
Bake for 12-15 minutes. Let cool completely before filling.
Make the Buttercream:
Beat softened butter with powdered sugar, adding espresso and hazelnut spread. Add a pinch of salt for balance.
Assemble:
Once shells are cool, pipe the buttercream onto one macaron shell and sandwich with another.
Chill and Serve:
Let the macarons rest in the fridge for at least 30 minutes to let flavors meld before serving.