Make the cake: Preheat the oven to 375˚. Lightly coat an 11-by-17-inch rimmed baking sheet with cooking spray, then line with parchment paper. Beat the egg yolks, brown sugar and vanilla and almond extracts in a medium bowl with a mixer on medium-high speed until thick and pale yellow, about 3 minutes.
Using clean beaters, beat the egg whites and salt in a large bowl with a mixer on medium speed until soft peaks form, about 1 minute. Gradually beat in the confectioners' sugar, then increase the speed to medium high and beat until stiff peaks form, 2 to 3 minutes. Fold one-quarter of the beaten egg whites into the egg yolk mixture with a rubber spatula. Gently fold the egg yolk mixture into the remaining egg whites until there are no more white streaks.
Whisk the two flours in a medium bowl and gently fold into the egg mixture until combined. Spread the batter in the prepared pan. Bake until a toothpick inserted into the center of the cake comes out clean, 13 to 15 minutes.
As soon as the cake comes out of the oven, dust with confectioners' sugar. Loosen the edges with a paring knife. Place another baking sheet on top of the cake and invert the cake onto it. Remove the top baking sheet and parchment. Dust more confectioners’ sugar on the exposed cake. Cover with a clean kitchen towel (not terry cloth) and place the baking sheet on top. Invert the cake again so it is on the towel and remove the top baking sheet. Starting at a long end, roll up the cake and the towel together to form a log. Place seam-side down on a rack and let cool, about 45 minutes.
Meanwhile, make the frosting: Beat the heavy cream, confectioners' sugar and salt in a large bowl with a mixer on medium-high speed until soft peaks form. Reduce the speed to medium and beat in the mascarpone and vanilla until thickened, about 30 seconds (do not overbeat). Refrigerate the frosting until the cake has cooled.
Gently unroll the cake with a long side facing you. Spread 1 1/2 cups frosting over the cake, leaving a 1/4-inch border on the two short sides and a 1-inch border on the far long side. Dollop the cherry jam on top and gently spread to cover the frosting. Reroll the cake (without the towel) and place seam-side down on a platter. Trim both ends, then cut off one 3/4-inch-thick slice. Unroll the slice slightly to cut off 3 inches of the spiral; reroll the slice into a spiral (this will be the knot of the log).
Frost the cake with all but 1/2 cup of the frosting, using a small offset spatula to create a bark-like texture. Place the small cake slice on the side to look like a tree knot; cover with the remaining frosting.
Put the chocolate in a small microwave-safe bowl and microwave in 30-second intervals, stirring, until smooth. Let cool, then transfer to a small resealable plastic bag and snip a corner. Pipe thin lines of chocolate onto the cake, pressing it into the frosting with the tip of the bag. Refrigerate the cake until ready to serve.