Start by making the dough: In a bowl, combine the butter and sugar. Beat with a hand mixer until creamy. Add the eggs, both flours, and enough unsweetened cocoa powder to make a dark dough.

After chilling, divide the dough in half. Roll each half between two sheets of parchment paper to about 1/8 inch (3 mm) thick. Use a round cookie cutter to cut out the cookie bases.

Place a generous teaspoon of Nutella in the center of half the cookies. Cover each with another cookie round and seal the edges well.

Place the Nutella Grisbì cookies on a baking sheet lined with parchment paper. Bake in a preheated static oven at 350°F (180°C) for exactly 10 minutes. Let cool, then dust generously with unsweetened cocoa powder.