Yule Log Yule Log (Bûche de Noël)

Make the Cake

1. Preheat oven to 350°F
2. In a medium bowl, mix together the flour, cocoa powder, baking powder, and salt. Set aside.
3. In the bowl of your stand mixer (or using a hand mixer and a bowl), add the room-temperature egg whites. Use the whisk attachment on HIGH to begin whipping the egg whites. After about 1 minute of whipping, gradually add ¼ cup of the sugar. Continue whipping on HIGH until soft peaks form, about 4 to 5 minutes. Remove the whisk attachment and use a spatula to transfer the egg whites to a large bowl. Use a paper towel to wipe out excess whites in the bowl (it doesn't need to be 100% clean).
4. Place the bowl back in the base of the mixer and re-attach the whisk. Place the egg yolks in the bowl and turn the mixer to HIGH. Beat the eggs for about 1 minute, and then gradually add the sugar, melted butter, and vanilla extract. Continue whipping on HIGH until the mixture is a pale yellow and thickened, about 4 minutes.
5. Remove the bowl and use a large spatula to fold in half of the whites and half of the flour mixture. Be gentle. It's okay if you see some white streaks from the egg whites. Fold in the rest of the egg whites and flour mixture. Gently mix until completely combined.
6. Spray the pan liberally with cooking spray. Place parchment paper on the pan and spray again with the cooking spray.
7. Gently transfer the batter from the bowl to the prepared pan. Use a spatula to softly smooth the batter to the edges of the pan.
8. Bake for 12 to 13 minutes, or until the edges of the cake just begin to pull away from the sides of the pan and the cake feels slightly spongey when pressed.
9. While the cake is baking, place a large smooth kitchen towel on a large cutting board or any smooth surface. Use a small sieve to dust cocoa powder liberally all over the towel.
10. Remove the cake from the oven onto a rack. Let rest for about 5 minutes (no longer). Use a sharp knife, or offset spatula, to run along the edge of the cake, helping to loosen it completely from the sides.
11. Carefully tip the pan on its side and use your hand to help guide the cake onto the prepared towel. (You may need to use a small towel to hold the pan since it will still be hot). Peel the parchment paper from the cake and discard.
12. Starting from the short side of the cake, use the towel to help you slowly and carefully roll the cake (with the towel). Let the cake rest (seam side down) in a cool place in your kitchen until completely cooled (1 to 2 hours).

Make the Sugared Cranberries and Rosemary Sprigs

1. Add the water and sugar to a medium-sized saucepan over medium heat. Once the water is hot, stir until the sugar has completely dissolved. Place the cranberries and rosemary in the water. Once fully coated, remove with a slotted spoon and place on a plate to dry for about 30 minutes, or up to several hours.
2. Add about ½ cup of sugar to a plate and place the cranberries and rosemary into the sugar, moving them around to fully coat. Place in the refrigerator until ready to garnish the cake.

Make the Cream Filling

1. Using a hand mixer (or your stand mixer), whip together the heavy cream, powdered sugar, and vanilla until stiff peaks form, about 3 to 5 minutes. Set aside.

Make the Chocolate Icing

1. About 1 hour before assembling the cake, make the icing by melting the butter in a medium saucepan over medium heat. Once the butter has melted, add the chocolate chips and stir until completely melted. Turn off the heat and stir in the sour cream.
2. Gradually add the powdered sugar, and continue stirring until completely combined and the icing has come together. Let rest until completely cool.

Assemble and Garnish the Cake

1. Once the cake is completely cooled, carefully unroll it on the cutting board. The ends of the cake will be slightly curled, this is normal.
2. Use a spatula to spread about a ¼-inch thick layer of the cream filling, leaving about a ½-inch border along the edges. You may not use all of the cream, don't add too thick a layer of the filling, otherwise, you'll have difficulty rolling the cake.
3. Using the towel to help, carefully roll the cake into a log (only use the towel to help you roll it somewhat tightly, don't let the towel roll with the cake).
4. If any excess filling was pressed out of the cake, use a knife to scrape it away and save it for another use.
5. Place the cake, seam side down, on your serving platter. Cover with plastic wrap and place in the refrigerator for 30 minutes, or up to overnight.
6. Remove the plastic wrap and if desired, use a large sharp knife to slice the ends off of the cake. You may need to use a small damp paper towel to clean up the ends if any of the cream filling is smeared over the sides of the cake.
7. Spread the icing all over the top and sides of the cake (you may not use all of the icing).
8. Use a fork to gently create streaks across the cake that resemble the bark on a tree. Place the sugared rosemary sprigs and cranberries on the top of the log and along the base of it. Use a fine-mesh sieve to sprinkle powdered sugar along the top of the log. Serve at once, or gently cover until ready to serve.