Melt the butter: Gently melt 150 g butter using a water bath (50–60°C) or in the microwave for 30 seconds, stirring until fully melted.

Mix with sugars: Add white sugar and brown sugar to the melted butter and stir until fully dissolved.

Add egg: Let the butter mixture cool to about 30°C (warm but not hot). Add the egg and whisk until smooth and glossy.

Combine dry ingredients: Sift in flour, cocoa powder, and baking powder. Fold gently until no dry spots remain. The dough should be soft and moist.

Chill: Cover with plastic wrap and refrigerate for 30 minutes. This helps the dough firm up and keeps the cookies from spreading too much.

Preheat oven: 180°C (350°F) for 10–15 minutes.

Shape: Divide dough into 60 g portions. Roll each into a ball and place them on a parchment-lined tray, spaced 3–4 cm apart.

Bake: Bake in the middle rack for about 15 minutes until the edges are dark and set but the centers remain soft.

Create the thumbprint: While still warm, use the back of a spoon or round tool to gently press a well in the center of each cookie.

Melt the ganache: Combine dark chocolate and heavy cream in a bowl. Place over hot water (50–60°C) and stir until smooth and glossy.

Fill: Let the ganache cool slightly, then spoon or pipe it into the wells of each cookie.

Decorate: Sprinkle chocolate shavings or shredded coconut on top. Let the ganache set for 10 minutes before serving.