Directions

• Center a rack in the oven and preheat the oven to 375 F. Butter an 8-inch springform pan, fit the bottom of the pan with a round of parchment or wax paper and grease the paper. Put the pan on a baking sheet lined with parchment or a silicone mat.
• For the cake
• Whisk together the nuts, flour and salt.
• Put the prunes and 1/4 cup of water (60 g) in a small saucepan over medium heat and cook, being careful not to scorch the fruit, until the water almost evaporates.
• Pull the pan from the heat and pour in the Bourbon, stand back and set it aflame. When the flames die out, transfer the fruit and any remaining liquid to a bowl and let cool. (If it’s more convenient, you can flame and steep the prunes up to 1 day ahead. Pack the prunes and their liquid into a covered jar and keep at room temperature.)
• Combine the chocolate, butter and 3 tablespoons water in a heatproof bowl, set it over a pan of simmering water over low heat and stir occasionally until the chocolate and butter are melted; or do this in a microwave oven. Remove the chocolate from the heat just as soon as it is melted and not very hot—you don’t want the chocolate and butter to separate.
• In a large bowl, whisk the egg yolks and sugar together until thick and pale, about 2 minutes. Switch to a rubber spatula and, one by one, stir in the chocolate and butter mixture, the nut mixture, and the prunes with any liquid.
• Working with a stand mixer fitted with the whisk attachment or with a hand mixer in a large bowl, beat the egg whites until they hold firm, glossy peaks. Stir about one quarter of the beaten whites into the chocolate mixture, then gently fold in the remaining whites. Turn the batter into the pan.
• Bake the cake for 28 to 32 minutes, or until it is puffed, firm on top and starting to come ever so slightly away from the sides of the pan; a thin knife inserted into the center will come out streaky — the cake should not be wet, but you don’t want it to be completely dry.
• Transfer the cake to a rack and let it cool for about 10 minutes, then carefully remove the sides of the pan. Invert the cake, pull off the paper and turn right side up to cool to room temperature. The cake should be absolutely cool before you glaze it.
• For the glaze
• Melt the chocolate in a heatproof bowl over a pan of gently simmering water, or in a microwave oven. Remove it from the heat and, using a small spatula, stir in the sugar, then the butter, a bit at a time, stirring until you have a smooth glaze.
• To finish the cake
• If the cake has crowned, use a long serrated knife and a gentle sawing motion to even the top. Turn the cake over onto a cooling rack— you want the very flat bottom of the cake to be the top. Put a piece of wax paper or foil under a cooling rack to serve as a drip catcher.
• Have a long metal icing spatula at hand. Pour the glaze over the top of the cake, allowing the excess to run down the sides, and use the spatula to smooth the top of the cake if necessary — usually the glaze is a self-spreader — and to even it around the sides of the cake. Let the glaze set at room temperature or, if you want to speed it up, slide the cake into the refrigerator for about 20 minutes.