- 1 1/4 cups vanilla sugar , divided
- 1/2 cup hazelnuts, lightly toasted, husked
- 6 large egg yolks (preferably organic)
- 1 cup (2 sticks) salted butter, melted
- 2 cups unbleached all purpose flour
- 1 large egg yolk beaten with 2 teaspoons water (for glaze)
- Whole strawberries with stems attached or warm strawberry jam
- Position rack in center of oven and preheat to 325°F. Butter and flour 9-inch-diameter springform pan. Combine 2 tablespoons vanilla sugar and hazelnuts in processor; blend until nuts are finely ground but not pasty. Combine 6 egg yolks and remaining 1 cup plus 2 tablespoons vanilla sugar in large bowl; whisk until well blended and slightly thicker, about 2 minutes (do not use electric mixer). Whisk in hazelnut mixture. Gradually whisk in melted butter. Sift flour over batter; stir just until blended (batter will be thick; do not overmix or cake may be tough).
- Transfer batter to prepared pan; smooth top with offset spatula (layer will be thin). Brush top generously with egg glaze. Using back of tines of fork, deeply mark crisscross pattern atop cake, marking 3 times across in 1 direction and 3 times in opposite direction. Bake cake until deep golden on top and tester inserted into center comes out clean, about 1 hour. Cool in pan on rack 15 minutes, then remove pan sides and cool cake completely. DO AHEAD Can be made 1 day ahead. Wrap in foil and store at room temperature.
- Cut cake into wedges and serve with whole strawberries or with warm strawberry jam.