The meringue mushrooms and sugared cranberries & rosemary are completely optional garnishes. The recipe below includes both. For all make-ahead instructions, see recipe notes. I recommend watching the video tutorial above and reading the full recipe below before beginning. There’s a lot of cooling down, chilling, and other moving parts here!
Sugared Cranberries & Rosemary (ideally night before)
Place cranberries and rosemary in a large bowl; set aside.
In a medium saucepan, bring 1 cup of sugar and the water to a boil and whisk until the sugar has dissolved.
Remove pan from the heat and allow to cool for 5 minutes.
Pour sugar syrup over the cranberries and rosemary and stir to combine.
Let the cranberries and rosemary sit at room temperature or in the refrigerator (lightly covered) for 6 hours or overnight. You’ll notice the sugar syrup is quite thick after this amount of time.
Drain the cranberries and rosemary from the syrup and pour 1 cup of sugar on top. Toss to coat.
Pour the sugared cranberries and rosemary on a parchment paper or silicone baking mat-lined baking sheet and let them dry for at least 2 hours at room temperature or in the refrigerator.
Cake
Preheat oven to 350°F (177°C).
Spray a 12×17 inch baking pan (I use a 15x21 inch fine with double whipped cream) with nonstick spray or grease with butter, so the parchment paper sticks.
Then line it with parchment paper so the cake seamlessly releases.
Spray or grease the parchment paper too. We want an extremely nonstick surface for this cake roll.
Whisk the cake flour, cocoa powder, baking powder, and salt together in a medium bowl. Set aside.
Using a hand mixer or a stand mixer fitted with whisk attachment, beat the egg whites and 1/2 cup (100g) sugar together on high speed for 4-5 minutes or until stiff peaks form.
Transfer to another bowl.
Using the same mixing bowl you just had the egg whites in (no need to clean it), add the egg yolks, remaining sugar, oil, and vanilla extract.
Beat together on high speed for 3-4 minutes or until thickened and light in color.
Add half of the whipped egg whites into the egg yolk mixture.
Beat on low speed for 10 seconds.
Repeat with remaining egg whites and beat on low for 10 seconds.
Add half of the flour mixture and beat on low or fold with a rubber spatula until combined.
Repeat with remaining flour mixture. Avoid over-mixing and deflating those egg whites. Batter will be very light.
Spread batter evenly into prepared pan.
Gently bang the pan on the counter a couple times to pop any air bubbles.
Bake for 15-16 minutes or until the cake springs back when lightly poked with your finger. Cake will look a little bubbly on top when it’s done. That’s ok. Avoid over-baking cake because it will crack if over-baked.
As the cake bakes, place a piece of parchment paper (larger than the cake) or a thin kitchen/tea towel flat on the counter.
Using a fine mesh sieve, dust parchment/towel with 3 Tablespoons (15g) of cocoa powder.
Once the cake comes out of the oven, quickly run a knife around the edges to loosen it.
Immediately invert it onto the parchment/towel.
Peel off the parchment paper that was on the bottom of the cake as it baked.
Starting with the narrow end, begin tightly rolling the hot cake up with the parchment/towel. Do this slowly and gently.The cake will be warm
Allow the cake to cool completely rolled up in the parchment/towel. Feel free to place it in the refrigerator to speed it up, about 3 hours and up to 1 day.
Meringue Mushrooms
Preheat oven to 200°F (93°C)
Line a large baking sheet with parchment paper or a silicone baking mat.
In a completely clean residue-free large glass or metal mixing bowl, using a handheld mixer or stand mixer fitted with a whisk attachment, beat the egg white, cream of tartar, and salt together on high speed until foamy, about 2 minutes.
With the mixer running on high speed, slowly add the sugar and beat until stiff glossy peaks form, about 2 more minutes.
Snip off the end of a plastic bag or fit a round piping tip in a piping bag. I use and recommend Wilton 2A piping tip or any tip with around a 1/2 inch opening.
Pipe quarter-sized circles (these will be the round mushroom tops) and 1-inch tall cones (these will be the stems).
Using a moistened finger (just a dab of water is fine), smooth down any peaks.
If desired, lightly dust mushroom tops with cocoa powder using a fine mesh sieve.
Bake for 2 hours. Do not open the oven as the meringues bake.
Turn off the oven after 2 hours and let the meringues sit inside the cooling oven for 20 minutes.
Remove meringues from the oven and cool completely.
When they’re just about cool, melt the 1 ounce of chocolate in a double boiler or use the microwave. If using the microwave, melt in 15 second increments, stopping and stirring between each until melted and smooth.
Cool for 5-10 minutes.
Once meringues have cooled, use a flat spatula to remove them from the baking sheets.
Dot a bit of chocolate onto the center of the bottom of a mushroom top. Adhere a mushroom stem to it.
Place back on the baking sheet to set. If stems or tops still have a little peak, scrape off with a knife or your spatula
Let chocolate cool and harden, about 1 hour
Whipped Cream and Assemble
Remove the cake roll from the refrigerator and allow to sit on the counter for a few minutes to warm up as you prepare the whipped cream.
Using a hand mixer or a stand mixer fitted with a whisk attachment, whip the heavy cream, Frangelico, confectioners’ sugar, and cocoa powder on medium-high speed until medium to stiff peaks form, about 2-3 minutes.
Gently and very slowly unroll the cake.
Spread whipped cream evenly on top, leaving about a 1/2 inch border around the cake.
Sprinkle chopped hazelnuts on top.
Gently roll the cake back up, without the parchment/towel this time. Roll it slowly. This part is messy.
Carefully place on a cutting board.
If the exterior of the cake looks moist, dust with a little cocoa powder.
Cover with plastic wrap and refrigerate for at least 30 minutes and up to 2 days before shaping and topping with ganache.
Ganache and Decorating
Place chopped chocolate in a medium bowl.
Heat the cream in a small saucepan until it begins to simmer. (Do not let it come to a rapid boil– that’s too hot.)
Pour over chocolate, then let it sit for 2-3 minutes to gently soften the chocolate.
Slowly stir until completely combined and chocolate has melted.
Ganache will be thin, so it has to thicken before using. Refrigerate, uncovered, for at least 30 minutes and up to 1 hour to thicken.
Remove rolled cake from the refrigerator.
Slowly pour and spread thickened ganache all over the top and sides of cake.
Use a fork to make textured lines resembling tree bark.
Feel free to wipe the serving plate if ganache dripped all over.
Decorate with meringue mushrooms, sugared cranberries and rosemary, and a dusting of confectioners’ sugar just before serving.
Cover leftover cake and store in the refrigerator for up to 3 days.