Hazelnut Gâteau Breton

Ingredients

• 1 large egg yolk with 2 teaspoons water (for glaze) beaten
• 6 large egg yolk organic (preferably )
• 0.5 cup hazelnuts husked lightly toasted
• 1 cup butter salted melted (2 sticks)
• 12 servings strawberry jam whole with stems attached or warm strawberry jam
• 2 cups unbleached all purpose flour 
• 1.3 cups tsp vanilla sugar divided

Equipment

• bowl
• frying pan
• oven
• whisk
• hand mixer
• aluminum foil
• springform pan
• offset spatula

Directions

1. Position rack in center of oven and preheat to 325°F. Butter and flour 9-inch-diameter springform pan.
2. Combine 2 tablespoons vanilla sugar and hazelnuts in processor; blend until nuts are finely ground but not pasty.
3. 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).
4. 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).
5. Transfer batter to prepared pan; smooth top with offset spatula (layer will be thin).
6. 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.
7. 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.
8. Cut cake into wedges and serve with whole strawberries or with warm strawberry jam.