For the chestnut cake, preheat the oven to 170 °C. Whisk sugar and egg yolks until very foamy. Stir the breadcrumbs and chestnut puree into the foam mixture.
Beat the egg whites with a pinch of salt until stiff and carefully fold into the above mixture. Pour everything into a 26 cm cake tin lined with baking paper and bake for 1 hour.
Whip the cream with cream stiffener until stiff, mix with sugar, vanilla sugar and chestnuts. Spread the cooled cake with the whipped cream and sprinkle with chocolate chips.