Preheat oven to 350 degrees F (180 degrees C).
Sift together Powdered Confectioners Sugar (200 gram), Almond Meal (110 gram), and Dark Cocoa Powder (2 tablespoon) in a large bowl. Stir to combine.
Bring the whites of the Egg (3) to room temperature, and beat in the bowl of a stand mixer with the whisk attachment until bubbly. Slowly add Granulated Sugar (50 gram), and continue to beat until soft peaks form.
Fold one quarter of the dry ingredients into the egg whites and gently fold in. Add in the rest of the dry ingredients, and fold in until fully combined.
Put batter into a pastry bag, and pipe into uniform rounds on a greased baking sheet. Bang tray down on a flat surface. Let sit for 1 hour. Once you can touch them without them sticking, they are ready for the oven.
Bake for 10 minutes.
Meanwhile, in a large bowl, add Heavy Cream (1/2 cup), Chocolate (56 gram), and Nutella® (3 tablespoon). Microwave 30 seconds,. Stir, and repeat until fully melted. Stir to combine. Refrigerate for 45 minutes, stirring every 15 minutes.
Beat mixture using a hand mixer for a few minutes. Then, put it into a pastry bag.
Pipe a glob onto half of the cooled cookies, and top with another cookie. Enjoy!