1-Step 1: Sugared Cranberries and Rosemary Begin with the garnishes to let them dry. Bring 3/4 cup water and 1 cup granulated sugar to a boil to form a syrup. Pour this over 1 cup fresh cranberries and 4-5 rosemary sprigs, letting them soak for several hours or overnight. Drain and coat with the remaining 1/4 cup sugar, then let dry at room temperature or in the fridge for up to 3 days.

2-Step 2: Preparing the Cake Preheat your oven to 350°F (175°C) and grease a jelly roll pan lined with parchment paper. Sift together 1 and 1/3 cups cake flour, 2 tablespoons unsweetened natural cocoa powder, 1 teaspoon baking powder, and 1/2 teaspoon salt. In one bowl, whip 6 large egg whites with 1/2 cup granulated sugar to stiff peaks. In another, beat the egg yolks with the remaining 1/2 cup sugar, 2 tablespoons vegetable oil, and 1 and 1/2 teaspoons pure vanilla extract until thick. Gently fold half the egg whites into the yolk mixture, then add half the dry ingredients. Repeat with the rest, being careful not to deflate the batter. Spread it evenly in the pan, tap to remove air bubbles, and bake for 15-16 minutes until springy.

3-Step 3: Rolling the Cake While the cake is warm, dust a kitchen towel with 3 tablespoons unsweetened natural cocoa powder. Invert the cake onto it, remove the parchment, and roll it up gently. Let it cool completely, and refrigerate if needed to make assembly easier. This step helps prevent cracks and keeps the shape intact.

4-Step 4: Meringue Mushrooms Preheat the oven to 200°F (93°C). Whip 1 large egg white with a pinch of salt and less than 1/8 teaspoon cream of tartar until foamy, then gradually add 2 tablespoons granulated sugar to form stiff peaks. Pipe small caps and stems on parchment paper, dust the caps with 1/2 teaspoon unsweetened natural cocoa powder if desired, and bake for 2 hours. Let them cool in the oven for 20 minutes, then attach the caps to stems with melted 1 ounce semi-sweet chocolate.

5-Step 5: Cocoa Hazelnut Whipped Cream Whip 1 and 1/2 cups cold heavy cream with 2 tablespoons liqueur, 1/4 cup confectioners’ sugar, and 1 tablespoon unsweetened natural cocoa powder to medium-firm peaks. Fold in 1/2 cup finely chopped hazelnuts if using. This creamy filling adds a nutty twist that complements the cake perfectly.

6-Step 6: Assembling and Ganache Unroll the cooled cake and spread the whipped cream, leaving a 1/2 inch border. Sprinkle extra hazelnuts, roll it up again, and chill for at least 30 minutes. For the ganache, heat 3/4 cup heavy cream to a simmer, pour over 6 ounces finely chopped semi-sweet chocolate, and stir until smooth. Cool in the fridge for 30 minutes to 1 hour, then spread over the cake and use a fork to create a bark texture. Decorate with meringue mushrooms, sugared cranberries, and rosemary. As noted in a related baking guide, preparing ahead can make the process more enjoyable.