This jelly roll recipe uses the moistest and richest of all sponges--the chiffon cake--as the platform for a filling of apricot and mascarpone cream. The trick to getting the perfect spiral without breaking the cake is to "train" it by rolling it in a tea towel while still warm, forming a rolled memory while it cools. Then the cake can be filled and re-rolled easily.
a quarter sheet pan, a piping bag with a large star tip
Preheat the oven to 350 degrees F. Bring a small saucepan of water to a boil.
For the chiffon cake: In a medium bowl, whisk together the cake flour and 1/4 cup of the sugar. Add the baking powder and salt to the bowl and whisk together. Set aside.
In a separate bowl, whisk together the 3 egg yolks, milk, vegetable oil and vanilla until combined.
Add the wet mixture to the dry ingredients and whisk together to form a loose batter. Be sure to continue whisking until all the clumps of flour have been completely incorporated and the batter is smooth. Fold in the yellow food coloring to reach the desired color. Set aside.
Meanwhile, add the 4 egg whites to the bowl of a stand mixer fitted with a whisk attachment and begin to beat on medium speed until foamy. Add the cream of tartar and continue beating. Begin slowly streaming in the remaining 1/2 cup sugar and continue beating until the meringue holds stiff, glossy peaks, 2 to 3 minutes.
With a rubber spatula, incorporate a third of the meringue into your batter, folding it in to preserve as much air in the egg whites as possible. Gently fold in the remaining meringue and continue to stir until completely incorporated.
Line a quarter sheet pan with parchment paper and butter the parchment and the sides of the pan. Pour in the cake batter and smooth out to fill all the corners. Bake until a cake tester comes out clean, about 15 minutes.
While the cake is baking, prepare your fillings: Melt the white chocolate in a medium heatproof bowl set over a small saucepan of simmering water (don't let the bowl touch the water). When the chocolate is melted, allow it to cool slightly and whisk in the mascarpone and confectioners' sugar. Remove one cup of this mixture and add to a piping bag fitted with a star tip.
Before the cake comes out of the oven, dust a tea towel larger than the pan with a nice layer of confectioners' sugar. When cake is done, using a knife, loosen the sides of the cake from the pan. While the cake is still warm, invert it onto the prepared tea towel and carefully remove the parchment paper. Roll up the cake with the tea towel from short end to short end and move onto a wire rack and to cool, seam-side down, for 20 minutes.
While the cake is still somewhat warm, unroll it and smear the inside with a thick layer of apricot jam.
On top of the jam, add the mascarpone filling from the bowl (save what is in the piping bag for decorating at the end). Cover the jam with mascarpone filling from end to end.
Reroll the cake, removing the tea towel as you roll. Allow the cake to completely cool and set, seam-side down.
Decorate the cake by piping the remaining mascarpone mixture down center of the cake and around the base. Add white chocolate curls all over.
Unrolling the cake while still a little warm and adding filling will prevent it from cracking too much.