Clad in a satiny chocolate glaze and rolled with chestnut mousse, this black-tie cake with gold leaf-adorned chestnuts is fitting for New Year's Eve. It can be made a day ahead, leaving you plenty of time to dress to the nines, too.
- Vegetable-oil cooking spray
- 1/4 cup unsweetened cocoa powder, plus more for dusting
- 1/2 cup cake flour (not self-rising)
- 2 tablespoons cornstarch
- Pinch of salt
- 4 large eggs
- 1/2 cup sugar
- 3 tablespoons unsalted butter, melted
- Armagnac Syrup
- Chestnut Mousse
- Chocolate Glaze
- Chestnuts, in syrup, drained, for garnish
Preheat oven to 375 degrees. Coat a 13-by-18-inch rimmed jelly-roll pan with cooking spray; line with parchment. Coat lining with cooking spray. Dust with cocoa; tap out excess. Sift cocoa, flour, cornstarch, and salt together into a bowl; set aside.
Put eggs and sugar in the heatproof bowl of an electric mixer; set over a pan of simmering water. Whisk constantly until sugar is dissolved and eggs are hot to the touch. Transfer bowl to mixer fitted with the whisk attachment. Beat on high speed until pale, fluffy, and cool.
Sprinkle flour mixture over egg mixture; gently fold in with a rubber spatula. When almost combined, pour melted butter down side of bowl; fold in. Pour batter onto pan; smooth. Bake until cake pulls away from sides of pan and is springy to the touch, 8 to 10 minutes.
Run a thin knife around cake. Invert onto a clean kitchen towel dusted generously with cocoa; peel off parchment.
Starting from one short end, roll cake, using towel to guide into a log. Transfer to a wire rack; let cool completely.
Unroll cake. Brush surface with Armagnac syrup; then spread with mousse, leaving a 1/2-inch border. Roll up again, using kitchen towel. Bring towel's edges together along top of cake; secure with clothespins (leave ends open). Refrigerate at least 4 hours or overnight.
Transfer cake to a rack set over a rimmed baking sheet; remove towel. Pour glaze on top. Refrigerate 30 minutes. Garnish with chestnuts, if desired.