Preheat the oven to 350°F and set the rack in the center of the oven. Grease and flour a 10-inch springform pan or cake pan and line the bottom with parchment paper.

Grind the hazelnuts:

Combine the hazelnuts and cornstarch in a food processor and grind to a fine flour. Set aside.

Cream the butter and incorporate the eggs (see the Notes on creaming butter and room-temperature eggs):

Place the butter in the bowl of the stand mixer with the paddle attachment and beat on medium speed for 1 minute. Add the sugar and hazelnut paste and beat on medium-high speed until the mixture becomes fluffy and lighter in color, 6 to 8 minutes, stopping the mixer occasionally to scrape down the sides of the bowl. Add the eggs, one at a time, and continue to beat until they are fully incorporated and the batter looks smooth and glossy, 1 to 2 minutes.

Prepare the dry ingredient:

In a small bowl, whisk together all the remaining dry ingredients and the ground hazelnuts.

Combine the dry ingredients and the crème fraîche:

With the mixer on slow speed, add half the dry ingredients to the butter and beat until the flour is just incorporated. Add all of the crème fraîche and continue mixing on slow speed. Add the rest of the dry ingredients, mixing until the batter is thoroughly combined. Scrape down the sides and bottom of the bowl with a rubber spatula and briefly beat on medium speed for 20 seconds.

Bake the cake:

Scrape the batter into the prepared pan, evening the batter with a rubber spatula. Run a paring knife in a single circular motion through the batter, 1 inch from the edge of the pan. This will help the cake to rise evenly. Bake the cake until a tester inserted in the middle of the cake comes out clean and the center is slightly springy, 50 to 60 minutes. If the center of the cake is still jiggly, bake another 10 minutes. Remove from the oven and allow to cool on a wire rack for 20 minutes. Invert the cake to remove it from the pan, and allow it to cool to room temperature.

Serving Suggestions:

Serve this cake warm with a sprinkling of powdered sugar; whipped cream or crème fraîche are also good accompaniments. If you are a lover of gianduja chocolate--the Swiss term for a hazelnut chocolate combination--ice this cake with Milk Chocolate Frosting. Or go all the way and serve it with Roasted Glazed Peaches doused with the peach’s roasting liquids, and topped with Sauternes Sabayon and Hazelnut Streusel.

Storage

This cake will keep, wrapped and at room temperature, for 4 days.