2ouncesfinely chopped dark milk chocolate(about 1/2 cup)
optional for serving:
unsweetened whipped cream
Position a rack in the center of the oven and preheat to 350º. Using the 1 tablespoon of butter, grease an 8" round cake pan, line the bottom with a round of parchment, then butter the parchment. Dust with the 1 tablespoon cocoa powder, turning the pan to coat it evenly and tapping out the excess. Set aside.
Roast the hazelnuts in the oven for 10-12 minutes, until fragrant and toasted. Let cool slightly, then rub between your palms or a tea towel to remove most of the skins. Let cool completely.
Place the remaining butter in a medium saucepan. Split the vanilla bean lengthwise, scrape out the seeds with the dull side of a knife, and add the pod and scrapings to the butter. Cook over medium heat, swirling occasionally, until the butter browns and smells nutty, 8 - 10 minutes. The butter will foam up, and the milk solids on the bottom of the pan should be a rich brown color. The rest of the butter will remain golden-amber. Watch it carefully, as it can go from brown to burnt in little time. Remove from the heat and let cool sightly.
In a food processor, combine the cooled nuts, flour, cocoa powder and salt. Grind very finely.
In a large metal bowl, whisk together the whites and the two sugars. Place over a water bath or directly over a low flame if you're feeling butch (but be careful!) and stir constantly with a whisk until the mixture feels warm to the touch and the sugar is mostly dissolved. Remove from the heat, and whisk in the almond mixture. Place the bowl on a damp towel to secure, and gradually whisk in the warm butter, 1/4 cup at a time, so that the mixture emulsifies. Fold in the chopped chocolate. The batter will be fairly liquid. It can be baked now, or allowed to hang out in the fridge for up to several days.
Pour into the prepared pan. Bake the cake for 30 - 40 minutes, until the top springs back when pressed lightly. Remove from the oven and let cool for 10 or 20 minutes. Loosen the edges with a small spatula if necessary. Place a large plate over the pan, grasp with bemitted hands, and flip the whole thing over to invert. Remove the pan and peel off the parchment. Let the cake cool a bit more. Serve warm or at room temperature.
The cake will keep for several days at room temperature, or up to a week in the fridge.
Feel free to substitute finely chopped dark or even unsweetened chocolate for the milk, and almonds for the hazelnuts. For a truly chocophilic experience, spread the cooled cake with a hazelnut liquor-spiked chocolate glaze.Nutritional values are based on one of ten servings.