Hazelnut Gâteau Breton

Directions

1. 1
   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).
2. 2
   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
3. 3
   Cut cake into wedges and serve with whole strawberries or with warm strawberry jam.