Hazelnuts are the star of the show in this cake from Italy's Piedmont region. Be sure to use fresh nuts, and toast them before grinding (see NOTE). In this recipe, I used a combination of melted butter and hazelnut oil. Hazelnut oil is expensive, but I happened to have some in my fridge from previous recipe testing. If you don't have it or would rather not spend the money to buy it, just use butter. Dust the cake with confectioners' sugar right before serving, and serve with warm sweetened heavy cream.
- 8 tablespoons unsalted butter, melted; OR 6 tablespoons melted unsalted butter and 2 tablespoons hazelnut oil (see NOTES)
- 2 1/2 cups toasted, skinned hazelnuts, cooled (see NOTES)
- 1/2 cup unbleached all-purpose flour
- 1 packet lievito pane degli angeli or 2 teaspoons baking powder (see NOTES)
- 4 eggs, separated
- 1 cup sugar
- Pinch of fine salt
- Confectioners' sugar for dusting
- Warm heavy cream sweetened with sugar (optional)
Heat the oven to 350 degrees. Coat a 9-inch cake pan with about 1 tablespoon of the melted butter. Place a round of parchment paper in the bottom of the pan and coat the parchment with butter. Set the remaining melted butter aside.
Process the cooled toasted hazelnuts in a food processor fitted with the metal blade until they are finely ground. Take care not to let them get pasty. Transfer them to a bowl and stir in the flour and baking powder. Set aside.
In a large bowl, whisk together the egg yolks and sugar. The mixture will be very thick and cling to the whisk. Drizzle in the remaining melted butter (or melted butter and hazelnut oil, if using), a little at a time, whisking all the while, until the butter has been fully incorporated.
Using a sturdy silicone spatula, stir the hazelnut-flour mixture into the egg yolk-butter mixture. It will be as thick as nut paste. This is fine.
In a clean, stainless steel bowl, beat the egg whites and salt until stiff peaks form. Scoop about 1/4 of the egg whites into the bowl with the nut paste mixture and begin stirring and folding it in with the spatula. This will help to loosen the batter a bit. Add half of the remaining egg whites, folding rather than stirring them into the batter to prevent them from deflating too much (the batter will still be thick and sticky). Finally, add the last of the whites and continue folding until they are incorporated into the batter (there may be a few streaks here and there). The batter will be thick but spreadable. Scrape it into the prepared pan and smooth out the top.
Bake the cake for 40 to 45 minutes, until puffed and browned on top and the center is no longer jiggling (a cake tester inserted in the center should come out clean). Be careful not to jostle the cake when you're checking for doneness!
Transfer the cake to a cooling rack and let cool in the pan for 30 minutes. Invert the cake onto a plate or another rack and peel off the parchment. Re-invert and let cool completely. Serve dusted with confectioners' sugar and with warm sweetened cream for drizzling.
Hazelnut oil is available in many supermarkets. It is not cheap (about $8.00 for 250 ml/8.45 oz) but it really enhances the nut flavor of the cake. It's also delicious drizzled on salad greens. I happened to have some in my fridge, which is why I used it in this recipe. It's an optional splurge and the cake will still be delicious even if you leave it out.
To toast and skin hazelnuts: Heat the oven to 350 degrees F. Spread the shelled nuts on a rimmed baking sheet and bake 10 minutes, or until the skins have begun to crack. Wrap the hot nuts in a clean kitchen towel and let stand 1 minute. Roll the nuts back and forth in the towel to loosen and rub off the skins. Not all the skins will come off, which is fine. Let cool before processing.
Lievito pane degli angeli is a vanilla-scented powdered leavening agent used in Italian baking. It's sold in packets and found in most Italian groceries. You can substitute 2 teaspoons baking powder.