Marjolaine

Preheat the oven to 350°F (180°C). Line two 11-by-17-inch (28-by-43-cm) rimmed baking sheets with parchment paper.

To make the cake base, spread the hazelnut powder on another rimmed baking sheet, place in the oven, and bake for about 5 minutes, or until it smells like roasting nuts. Remove from the oven and pour into a bowl to cool.

In a stand mixer fitted with the whip attachment (or by hand with determination), whip together the eggs and 1⅔ cups (180 g) of the powdered sugar until white and creamy. Using a rubber spatula, fold in the hazelnut powder and flour just until thoroughly combined. Transfer the mixture to a large bowl, and rinse the whip attachment and the mixer bowl. Dry thoroughly.