This triple chocolate vegan Yule Log is decadent, fun and deceptively simple to make. A silky chocolate mousse is rolled up in a tender chocolate sponge cake, and the whole thing is covered in a rich chocolate ganache. This seasonally decorative dessert that will have everyone at your table swooning for more.
Preheat the oven to 350°F. Line a 15" x 10" jelly roll pan (or cookie sheet with sides) with parchment paper. Spray the sides and parchment lightly with oil.
Wipe the stand-mixer bowl (or a medium bowl if you're using a hand-held beater) lightly with vinegar and dry. Add the aquafaba and vinegar, and beat on high until stiff peaks form, about 3-7 minutes depending on the appliance.
In a large bowl, sift in the flour, cocoa powder, sugar, salt, baking powder and baking soda. Whisk well. In a small bowl, combine the oil, hot liquid and vanilla extract.
Add the liquid ingredients to the dry ingredients, mixing just until blended. The batter will be very thick and some flour may remain, don't stress! Add about a cup of the whipped aquafaba, folding the mixture rather than stirring so you don't lose all of the air you've trapped in the aquafaba. If you've made macarons before, this is a similar process. Add the rest of the aquafaba, folding gently until the mixture is even. There may be a few small lumps but this is fine.
Pour the mixture on the prepared baking pan, smoothing out the batter to the edges. Bake in the preheated oven for 12-15 minutes or until a toothpick comes out clean or with a few cooked crumbs on it.
As soon as the cake comes out of the oven, place the tray on a cooling rack and gently cover the whole thing with foil. This will trap the moisture so the cake cracks less when you go to make the log. Let cool completely before assembling.
For the Chocolate Mousse:
Melt the chocolate. You can do this in a double boiler, or in the microwave in 30 second bursts, stirring well each time you check it. Do not overheat or it will seize and become unusable. Let cool until just warm, not hot.
Combine the drained tofu, maple syrup, rum (if using) and vanilla extract in a blender. Blend on high until smooth and silky. Add the melted chocolate and blend again until well combined. Cover with plastic wrap and place in the fridge for 30-45 minutes to cool and thicken.
For the Ganache:
Heat the coconut milk in a small pot over low heat. Stir in the chocolate, and whisk constantly until smooth and shiny. Remove from heat and set aside to lower to room temperature.
To Assemble the Log:
Slowly and gently peel the foil from the cake. A bit of the "skin" of the cake might come off, this is fine. Spread the mousse evenly over the cake. Cover with plastic wrap and place in the fridge for about an hour so that the mousse firms up.
Starting at the long side of the cake, roll the cake over the filling firmly but gently. If it tears a bit, the tears will be covered with ganache later. Keep rolling, slowly releasing the parchment paper as you go and using it to help roll the log over and down. When you get to the end, roll the log onto its seam and roll the parchment paper back around it (the last bit of parchment will not have been peeled off the cake). Keeping the log on the tray and wrapping in plastic, store in the fridge until completely chilled 2-3 hours, or overnight. Having it chilled will make it easier to decorate.
Remove the cake from the fridge. Cut 1 or 2 small pieces off the log at a 45° angle. Place the log on the serving tray, and position the angled side of the branches on the log for a cut branch effect. Use toothpicks or cut straws for support if necessary.
Using a pastry brush or small frosting spatula, cover the cake in ganache. Don't worry about making it smooth, some roughness creates a nice bark effect. Brush from one end of the log to the other to create bark lines. For the cut ends, swirl the ganache in a circular fashion, or wait until it's almost set up and use the tip of a skewer to create growth rings.
Create moss along the base of the log and in spots where the branches connect with the log by mixing finely chopped nuts with matcha powder. Store in the fridge until serving time.
To serve, sprinkle with confectioner's sugar and coarse white decorative sugar crystals for a snowy effect. If decorating with mushroom cookie meringues, apply them with bit of melted chocolate to "glue" them to the log.
*Aquafaba varies in thickness and protein content between homemade and storebought, between brands, and even cans from the same brand. Drain the chickpeas, measure the aquafaba and the bring to a simmer on the stove. Reduce the volume by 1/3-1/2. I have found doing so by 1/2 gives the best, more consistent results for sponges and meringues. Strain with fine mesh strainer and chill. It should have the consistency of egg whites once cold.**Coconut cream can be found in stores as is. If you can only find coconut milk, get the kind with no gums in it, chill it overnight and then scoop the fat off the top, saving the water for another use.