Yule Log (Bûche de Noël)

Preheat the oven to 375°F (190°C) and set an oven rack in the middle position. Lightly spray a 12 × 17-in (30 x 43-cm) jelly roll pan with nonstick spray, including the sides. Line the pan with parchment paper, running it up just the short sides. (Check to make sure the parchment isn’t climbing up the long sides—if it is, trim it so it fits neatly. Extra parchment on the long sides can cause the cake to wrinkle as it bakes.) Press the parchment firmly into the corners so it lays flat, then lightly spray the parchment with nonstick spray.

Make the Cake: In the bowl of an electric mixer fitted with the whisk or beaters, beat the egg yolks and ½ cup (100 g) of the sugar on medium-high speed until pale, thick, and ribbony when you lift the whisk/beaters, about 4 minutes (it will be the color of butter). Add the cocoa powder, vanilla, and salt and beat on medium-low speed until smooth, scraping down the sides of the bowl as needed.

In a separate clean, dry bowl, beat the egg whites on medium speed until soft peaks form, 1 to 2 minutes. Gradually add the remaining ¼ cup (50 g) sugar and continue beating on medium-high speed until glossy, stiff peaks form, 2 to 3 minutes more. You'll know it's ready when you lift the whisk out of the bowl and the meringue holds a firm peak with just a slight curl at the tip.

Using a large rubber spatula, gently fold the yolk mixture into the whipped egg whites in three additions, just until no white streaks remain. Take care not to deflate the batter.

Spread the batter evenly in the prepared pan, smoothing the top with an offset spatula. Bake for 10 to 12 minutes, or until the cake is puffy, set, and springs back when lightly touched.

Invert the Cake: As soon as the cake comes out of the oven, run a thin knife carefully along the long edges to loosen it from the pan—this step is important so the cake doesn’t tear when you invert it. Dust the surface of the warm cake generously with confectioners’ sugar to help prevent it from sticking to the towel as it cools. Lay a clean, lint-free kitchen towel directly on top—avoid anything with texture, which can imprint on the cake. Hold the towel firmly against the edges of the pan, then invert the whole thing in one quick motion onto the counter so the towel ends up on the bottom and the cake is upside down on it. Gently lift off the pan, then slowly peel away the parchment while the cake is still warm (you may need to nudge it a bit at the edges). Don’t worry if a thin film sticks to the paper—that’s normal for this delicate cake.

Roll the Cake: Starting from the short end near the edge of the towel, roll the warm cake and towel up together into a tight spiral (the towel prevents sticking). Rolling the cake while it’s still warm “trains” it to hold its shape later when filled. If there’s extra towel before you reach the cake, just roll it up a bit first, then continue rolling over the cake. Place the roll seam side down and let it cool completely, about 30 minutes.

Make the Filling: In the bowl of an electric mixer fitted with the paddle attachment or beaters, beat the softened cream cheese on medium speed until completely smooth, about 30 seconds. Add the sugar and cocoa powder and beat until fully combined and smooth, scraping down the bowl as needed, about 30 seconds more. Add the cream, vanilla, and rum (if using), and beat on medium speed until thickened to a spreadable consistency, scraping down the bowl as needed, 1½ to 2 minutes.

Fill & Roll: Gently unroll the cooled cake. Spread the whipped filling evenly over the cake, leaving a 1-in (2.5-cm) border around the edges. Re-roll the cake, this time without the towel, and place it seam side down on a serving platter. Refrigerate, uncovered, until chilled and set, at least 1 hour.

Make the Frosting: In a small saucepan, bring the heavy cream just to a simmer over medium heat. Place the chopped chocolate in a medium bowl. Pour the hot cream over top and let sit for 1 minute to melt. Whisk gently until the chocolate is fully melted and the mixture is smooth and glossy. Mix in the rum (if using) and salt. Cover and refrigerate until the ganache is thickened and cold but still soft — about 1 hour. It should be scoopable but not firm. Using an electric mixer, beat the chilled ganache on medium speed until it lightens in color and becomes fluffy and spreadable, 45 seconds to 1 minute. Do not overbeat.

Decorate: Using a sharp serrated knife, cut a 2 to 3-in (5 to 7.5-cm) diagonal slice off one end of the roll. Place the cut piece along the side of the cake—about one-third of the way down—with the diagonal cut side facing in to form a branch.

Place parchment strips (about 2 inc/5-cm wide) around the edges of the cake. (The strips act as a shield to catch any excess ganache and keep the platter clean.)

Dollop about half of the whipped ganache on top of the cake. Using a small offset spatula or butter knife, spread it evenly over the top, sides, and branch, adding more as needed. For a classic “log” effect, drag the spatula or knife through the ganache to create bark-like ridges.

Arrange the meringue mushrooms in small clusters on top of and around the cake, gently pressing some into the ganache so they look “rooted.” Use any leftover whipped ganache to “glue” a few mushrooms to the platter, then nestle the sugared cranberries in small clusters along the base of the cake and here and there on top for a pop of color and sparkle. Finally, dust the whole cake lightly with confectioners’ sugar to mimic freshly fallen snow.

Cover the roll with an inverted container to protect the glaze without smudging it — a large bowl, roasting pan, or the dome of a cake carrier all work well. Refrigerate until ready to serve; it will keep nicely for up to 2 days. For the best texture and flavor, let it sit at room temperature for 20 to 30 minutes before serving—just long enough for the ganache to soften slightly, but not so long that the whipped cream filling warms up.