Roulade au Chocolat Pour Julia

Ingredients:
1 1/2 cups plus 2 tablespoons granulated sugar, 1 cup all-purpose flour, 3/4 cup unsweetened cocoa powder, 2 teaspoons baking powder, 1 teaspoon baking soda, 1/4 teaspoon salt, 4 eggs, separated, 3/4 cup vegetable oil, 1/2 cup water, 1 teaspoon vanilla extract, 2 egg whites, Chocolate-hazelnut mousse

Instructions:
1. Position the rack in the center of the oven and preheat the oven to 350 degrees. Butter or coat with vegetable spray a baking tray, 12 x 17 x 2 inches. Line with parchment paper and then spray the paper. Set aside.
2. Sift together 1 cup of the sugar, the flour, cocoa, baking powder, baking soda, and salt. Set aside.
3. In the large bowl of an electric mixer fitted with a paddle or beaters, beat the egg yolks at high speed. Turn the machine to low and pour in the oil, water, and vanilla. Gradually add the sifted ingredients and, when almost incorporated, turn the speed to medium and beat until well combined.
4. In another clean large bowl, with whip or clean beaters, whip the 6 egg whites until soft peaks form. Start on medium speed and raise the speed as the peaks begin to form. Gradually pour in the remaining 1/2 cup sugar and continue to whip until the whites are shiny and firm, but not stiff. With a rubber spatula, fold one-quarter of the whites into the chocolate mixture, then scrape the chocolate mixture back into the whites, quickly folding until completely incorporated.
5. Scrape into the prepared pan and spread with an offset spatula, smoothing and leveling the top. Bake until the edges of the cake pull away from the pan and the cake springs back when lightly pressed, 25 to 30 minutes. Cool on a rack.
6. When completely cool, place the pan on a firm surface. With a sharp knife, cut around the outside edges of the entire cake, separating the cake from the pan. Sprinkle 2 tablespoons of granulated sugar over the surface of the cake (to prevent sticking when you invert the cake). Invert a second baking tray on the top of the cake and flip the cake over onto the second tray. Carefully peel off the parchment paper, turn the paper over, and place back on the cake. Invert the cake and the paper so that the paper is on the baking tray and the sugared side is on top. You are now ready to spread the filling onto the cake.
7. Fill and roll the cake: Place the cake with one of the 17-inch sides directly in front of you. Using your spatula, spread 11 2 cups of the Chocolate-Hazelnut Mousse over the surface of the cake to the edge of three of the sides, leaving about a 1-inch space along the one side directly in front of you (see photo). Level the filling. Refrigerate the remaining mousse, covered.
8. Starting with the 17-inch side in front of you, using the parchment paper to help you, roll the cake toward the opposite side, completely enclosing the filling (see photo). Make certain that you do not roll the paper into the cake. Tuck the paper around the rolled cake to secure (see photo). Leave the cake on the pan and refrigerate until the filling is firm, at least 2 hours, up to overnight.
9. To serve, remove the cake from the refrigerator and unroll out of the paper onto a firm surface. Using a long serrated knife, cut a 2-inch diagonal piece off each end. With a #3 star tip fitted into a pastry bag, pipe 10 or 12 rosettes of mousse spaced evenly across the tip of the cake. Dust with sifted confectioners' sugar. Carefully transfer to a serving platter and refrigerate until needed. When ready to serve, cut into 10 or 12 portions. Pass the remaining mousse.