LEMON-POPPY SEED ROLL CAKE WITH WHIPPED STRAWBERRY MASCARPONE
- Position a rack in the center of the oven and heat the oven to 350°F (180°C /gas 4). Lightly grease the sides and bottoms of a 13x18x1-inch (33x46x2.5 cm) half sheet pan and line the bottom with parchment. Lightly grease and flour the parchment and lightly flour the sides of the pan.
- Put 3/4 cup (5 1/4 oz./149g) of the sugar and the lemon zest in a blender or food process and pulse until the zest is finely chopped and the sugar is fragrant. Sift the cake flour into the bowl of stand mixer fitted with the paddle attachment mixer (or in a large bowl using an electric handheld mixer fitted with wire beaters), add the lemon-sugar, baking powder and salt and whisk until blended. Add the egg yolks, oil, buttermilk and vanilla. Beat on medium-low speed until blended. Increase the speed to medium high and beat until lighter in color and thin enough to form a ribbon of batter in the bowl when the beater is lifted, 3 minutes. Add the poppy seeds and mix briefly until blended.
- Put the egg whites in the bowl of a stand mixer fitted with the whisk attachment (or in a large bowl using an electric handheld mixer fitted with wire beaters) and beat on medium-low speed until foamy. Increasing speed to medium, and beat until whites are opaque and climbing about half way up the bowl (the tracks from the whisk will be beginning to hold their shape) forming very soft peaks. Continue beating while slowly adding the remaining 1/4 cup (1 3/4 oz./50g) granulated sugar. Beat until the whites are thick, shiny and form medium peaks. (The peaks should droop over gently.) Do not over beat or the whites won’t expand during baking and the batter won’t rise as high.
- Scrape about a quarter of the whites into the flour mixture and, using a large silicone spatula, gently stir until blended. The batter will become lighter and make it easier to fold in the remaining whites. Add the remaining whites and gently fold until just blended with no visible streaks of either the whites or batter. Scrape the batter into the prepared pan and, using an offset spatula, gently spread into an even layer. Bake until the cake is pale golden brown and the top springs back when lightly touched, 13 to 15 minutes.
- While the cake is baking, have ready two long strips of paper towels (two large squares per strip), the confectioners’ sugar for dusting, a fine- mesh sieve, and two large racks.
- Move the pan to a rack and run the tip of a small knife around the edges to loosen the cake from the pan. Let cool 10 minutes. Sift the confectioners’ sugar over the cake in a generous layer. Cover the top of the cake completely with the strips of paper towels and cover with a rack large enough to overhang the edges of the pan. Gripping both racks with towels and with the sheet pan sandwiched in between, flip the pan and racks to invert. Lift the pan from the cake and carefully peel away the parchment.
- Beginning on one short (or, to serve 16, long) side, roll up the cake and paper towel layer together. Do this while the cake is still war or it will crack. Arrange, seam side down (the seam will not be directly under the cake but just to the side facing down), on the rack and let cool completely.
- Hull the strawberries and cut each in half then each half in half or quarters, if large. You should have about 4 cups of chopped strawberries. Scrape about half of the berries into medium saucepan and the sugar and lemon juice. Bring to a boil over medium-low heat, stirring constantly, until the sugar is dissolved then reduce the heat to low and cook, stirring often, until the berries have released their juice and burst when lightly pressed with the spatula, about 6 minutes. Add the remaining berries and cook, stirring, until the syrup is thick and jam-like (you will have about 1 1/2 cups), 6 to 8 minutes. Slide the pan off the heat, let cool completely and refrigerate until chilled. For faster cooling, Scrape into a bowl and set the bowl over a larger bowl filled with ice and a little water, stirring and scraping the sides frequently.
- Put the mascarpone, heavy cream and salt in the bowl of a stand mixer fitted with the whisk attachment (or in a large bowl using an electric handheld mixer fitted with wire beaters) and beat on medium-low speed until blended and smooth, about 1 minute. Increase to medium-high speed and beat until thick enough to hold firm peaks when the beater is lifted, about 2 minutes. Add the cooled strawberry mixture and, using a silicone spatula, fold until just blended.
- Carefully unroll the cake and remove the paper towels. It will look a bit wavy, uneven and will be curled at one end. Scrape the filling onto the cake and, using an offset spatula, spread evenly over the cake to within 1/2 inch of one of the short sides, the two long edges and to 1 inch of the remaining short (or long) side. Beginning with the shorter side with the filling almost to the edge, gently roll the cake without the paper towels. Using a long metal spatula, place the cake, seam side down (the seam will not be directly under the cake but just to the side facing down), on a flat serving plate or board. Refrigerate for 2 hours then cover loosely and continue chill for another 2 hours or up to 12 hours before serving.
- About 30 minutes before serving, remove the cake from the refrigerator. Dust the top of the roll with additional confectioners’ sugar, if desired. Using a serrated knife, cut the cake on alternate angles into wedges about 2 inches thick at the widest end and serve with additional fresh strawberries, if desired.