In the Oven: Tunnel of Hazelnut Fudge Cake

Posting date is September 28th!

TUNNEL OF HAZELNUT FUDGE CAKE

2 cups hazelnuts, toasted and skinned
2 cups all-purpose flour
1 teaspoon salt
2 cups confectioners’ sugar, plus more for dusting
3⁄4 cup dark unsweetened cocoa powder (like Valrhona)
10 ounces (2 1⁄2 sticks) unsalted butter, at room temperature, cut into 1⁄2-inch cubes
1 cup granulated sugar
3⁄4 cup firmly packed dark brown sugar
3 large eggs, plus 3 large egg yolks
1⁄4 cup vegetable oil
1 tablespoon pure vanilla extract

Preheat the oven to 350 degrees F. Generously spray the inside of a 10-cup Bundt pan with nonstick cooking spray; alternatively, butter it thoroughly, dust it with cocoa powder, and knock out the excess cocoa.
In a food processor, pulse the nuts until they are somewhere between coarsely chopped and almost powdery (you do not want to pulse until they become nut butter).
Pour the chopped nuts into a medium bowl, add the flour and salt, and whisk until combined.
Sift together the confectioners’ sugar and cocoa powder into a small bowl.
In the bowl of a standing mixer fitted with the paddle attachment, beat the butter and both sugars until pale and fluffy. Scrape down the sides and bottom of the bowl, turn the mixer to low, and add the eggs and egg yolks, one at time, beating until just incorporated.
Add the oil and vanilla and beat until the batter is uniform. Add the confectioners’ sugar mixture and beat on low speed until just combined. Remove the bowl from the mixer and gently fold in the nut mixture.
Spoon the batter into the prepared pan, smooth the top, and bake for 38 to 45 minutes, rotating the pan halfway through the baking time. Very important note: due to the presence of the fudgy cake center you will not be able to test the cake for doneness using the traditional “toothpick test.” Instead, make sure your oven temperature is accurate and watch the time carefully. The cake is technically done when it just begins to pull away from the sides of the pan or when it springs back when gently pressed— though this is not a fail-safe test. My best advice is to keep an eye on this cake after the 35-minute mark and pull it out the moment you think it’s done.
Transfer the Bundt to a wire rack to cool for 2 hours in the pan. A great tip we picked up from a Shirley O. Corriher recipe: To prevent the cake from cracking and sinking (if you care about these things—it is the bottom of the cake after all), simply use your fingers to gently press the surface of the cake where it touches the inner and outer edges of the Bundt pan.
Gently loosen the sides of the cake from the pan and turn it out onto a serving platter.
Sprinkle with a little sifted confectioners’ sugar, if you like, and serve immediately.
Freeze any leftover cake, tightly covered, for up to 7 days. Before serving, let the cake come to almost room temperature (we think the leftovers taste better cold than at room temperature).