Any way you look at it, it's nice to have a rich, yet gluten-free bit of naughtiness to share around…
Chocolate Sponge Cake
12 egg yolks
1 1/2 cups sugar, divided
10 egg whites
1 cup cocoa powder, sifted
1/4 teaspoon salt
2 teaspoons vanilla or 1 teaspoon vanilla and 3 tablespoons orange liqueur
Preheat oven to 375º F.
Line a large jelly roll pan (sided cookie sheet, 14"x 20" or somewhat larger) with well-greased parchment. Also line an 8"x8" or 9"x9" shallow brownie pan the same way.*
In the bowl of a standing mixer, beat the egg yolks with 3/4 cup sugar on high until pale and fluffy (about 5 minutes). Add salt and vanilla, then beat in cocoa powder. Transfer to another bowl and set aside.
Thoroughly clean and dry mixing bowl and whisk. Beat egg whites on medium-high until they form soft peaks. While the mixer is still running, gradually add in remaining sugar about a tablespoon at a time until mixture is glossy and stiff peaks form.
Stir well about 1/4 of egg white mixture into egg yolk/cocoa mixture to make it a little lighter. Gently fold in the remaining egg whites.
Transfer the mixture to the prepared baking sheets, spreading the batter just barely even with the tops of the pans. Bake 10 (for the smaller) to 15 minutes, until cake springs back when touched at center.
Cool on rack. Cake will deflate slightly.
If making a buche de noël or other rolled cake, allow the large sheet cake to cool only about 5 minutes. Using a cooling rack or a larger flat cookie sheet and a towel dusted with cocoa powder, turn cake out of pan (be sure the cake is NOT centered in the towel, but to one side or the other, with only an inch or two extra border on the one side. Start by rolling the wider towel edge and then very gently roll the cake around it, and allow to cool completely while preparing your choice of creamy filling.
When cool, carefully unfurl the cake, spread the filling thickly, use the towel to re-roll as tightly as possible. Again using the towel, transfer the cake to cake plate, outer seam side down. If you like, you can serve lightly dusted with confectioner's sugar or superfine granulated sugar. Or slather it with your favorite ganache or frosting.
*I have updated this to include a second, small pan, because this recipe has consistently expanded beyond a single jelly roll pan's sides, leaving a "muffin top" effect which, while tasty on its own, makes rolling more difficult and a bit unattractive unless you dig out a good knife and trim it all to heck (which, I will concede, gives us tasty crumbs to nibble before the grand unveiling, but we're trying to avoid being naughty until after Christmas morning). I suggest saving the smaller cake for a later date, perhaps to use in a New Year's trifle, or freezing it until St. Valentine's Day and making something decadent without the added effort.