Prepare the Cake Pan:

1. Preheat your oven to 350°F (175°C). Line a 15×10-inch jelly roll pan with parchment paper, leaving a slight overhang on the short sides. Lightly grease the parchment with cooking spray or butter.

Make the Chocolate Sponge: 2. In a large mixing bowl, beat the egg yolks with ½ cup sugar using an electric mixer on high speed for 3-4 minutes until thick, pale yellow, and ribbony. Mix in the vanilla extract.

3. In a separate clean bowl with clean beaters, whip the egg whites with salt on medium speed until soft peaks form. Gradually add the remaining ¼ cup sugar while continuing to beat, then increase to high speed and beat until stiff, glossy peaks form (about 2-3 minutes total).
4. Sift the cocoa powder and flour together into a small bowl. Gently fold the cocoa mixture into the egg yolk mixture in three additions, being careful not to deflate the batter.
5. Fold one-third of the whipped egg whites into the chocolate mixture to lighten it, then gently fold in the remaining egg whites until just combined and no white streaks remain. Don’t overmix—some small lumps are fine.

Bake the Cake: 6. Pour the batter into the prepared pan and spread evenly into all corners using an offset spatula. The batter will be thin—this is correct.

7. Bake for 10-12 minutes, until the cake springs back when lightly touched and a toothpick inserted in the center comes out clean. Don’t overbake or the cake will crack when rolled.

Roll the Cake: 8. While the cake bakes, lay a clean kitchen towel flat on your counter and dust generously with powdered sugar.

9. As soon as the cake comes out of the oven, run a knife around the edges to loosen it. Immediately invert the hot cake onto the prepared towel. Carefully peel off the parchment paper.
10. Starting from one short end, roll the warm cake and towel together into a tight spiral. Place seam-side down on a cooling rack and let cool completely (about 30-45 minutes).

Make the Filling: 11. In a chilled bowl, beat the heavy cream, powdered sugar, and vanilla on medium speed until it starts to thicken. Increase to high speed and beat until stiff peaks form. Don’t overbeat or you’ll make butter. Refrigerate until ready to use.

Assemble the Log: 12. Once the cake is completely cool, carefully unroll it (it will want to keep its shape—this is good). Spread the whipped cream filling evenly over the cake, leaving a ½-inch border on all sides.

13. Re-roll the cake without the towel, starting from the same short end. Roll tightly but gently to avoid squeezing out the filling. Wrap in plastic wrap and refrigerate for at least 1 hour.

Make the Buttercream: 14. Beat the softened butter on medium-high speed for 2-3 minutes until fluffy and pale. Reduce speed to low and gradually add the powdered sugar and cocoa powder, beating until combined.

15. Add the heavy cream, vanilla, espresso powder (if using), and salt. Increase speed to high and beat for 3-4 minutes until light and fluffy. If the frosting seems too thick, add more cream one tablespoon at a time.

Decorate the Log: 16. Unwrap the chilled cake roll and trim about ½ inch from each end at an angle to create clean edges. Cut one of these pieces in half diagonally to create “branch” sections.

17. Place the main log seam-side down on a serving platter. Attach the branch pieces to the side of the log using a bit of buttercream as glue, positioning them to look like cut branches.
18. Cover the entire log and branches with chocolate buttercream, using an offset spatula. Run a fork lengthwise through the frosting to create bark-like texture. Leave the cut ends exposed to show the spiral pattern.
19. Refrigerate for at least 1 hour to set the frosting. Before serving, dust lightly with powdered sugar for a snowy effect and decorate with rosemary sprigs, sugared cranberries, or meringue mushrooms.