1. In a mixer, mix the flour, cocoa, and a pinch of salt. Gradually add the sugar and butter. Incorporate the egg yolks. Form a ball with the dough and refrigerate for 3 hours.

2. Roll out the dough to a thickness of 3 mm. Cut out 6 disks. Fill the buttered tartlet molds. Prick the bottoms lightly. Refrigerate for 20 minutes.

3. Preheat the oven to 210°C.

4. Chop the hazelnuts into large pieces. Melt the chocolate in a double boiler and let it cool.

5. Mix the hazelnut powder with the cornstarch. Beat the egg yolks until they become pale, with the icing sugar. Incorporate the melted chocolate, hazelnut powder, and whipped egg whites with a pinch of salt.

6. Divide the mixture into the tartlets and top with hazelnut pieces.

7. Bake for 15 minutes and reduce the temperature to 180°C; cook for 10 minutes.

8. Remove from the oven, let cool, and unmold onto a rack before serving warm.