How to Make It
Preheat oven to 350°. Place pitted prunes (soak in hot water for 30 minutes first, if you have time) in the bowl of a food processor. Add vanilla extract, and process until prunes are broken down into small pieces; set aside. Grease a 10-inch round cake pan. Place chocolate in a heatproof bowl, and microwave (in 1-minute intervals) until melted and smooth. Stir in butter and fold in the prune purée and ground hazelnuts. Beat eggs yolks with sugar with an electric mixer 4 minutes; fold into the chocolate mixture. Beat egg whites with salt with a clean whisk until stiff peaks form. Fold whites into the chocolate mixture in 3 batches. Pour batter into prepared pan, and smooth top. Bake 20 minutes, rotate pan, and continue baking 5–7 minutes. Let cool, cut into 12 slices, and serve.
Lucid Food (Ten Speed Press)