Make Ganache

1. Add butter and chocolate to a double boiler set over medium-low heat, whisking often until melted
2. Remove chocolate and butter from heat and gradually whisk in cream. Transfer to a medium bowl and set aside at room temperature, stirring occasionally until icing thickens (at least 2 hours)  

1. Preheat oven to 375°
2. Butter a 16½" × 12" heavy baking pan, then line with parchment paper, cut large enough to hang over sides of the pan by about 1".  Butter parchment paper again on top
3. Put chocolate in a large mixing bowl and set aside.  Heat cream in a saucepan over medium heat until it reaches a boil then pour over chocolate and whisk until smooth. Set aside to cool
4. Add egg whites to the bowl of a standing mixer fitted with a whisk attachment. Whip on medium speed until frothy; increase speed to medium-high and gradually add sugar, beating constantly. Increase speed to high and beat until stiff, glossy peaks form
5. Mix one-third of the whites into chocolate using a rubber spatula, then gently fold in remaining whites in two batches, taking care not to deflate batter
6. Spread in prepared pan and bake until a toothpick inserted in center comes out clean, 10–12 minutes. Set aside to cool in the pan

1. Place cold heavy cream into cold mixing bowl
2. Start mixer on low speed. When it starts to gain a little volume, increase to medium speed. Slowly add powdered sugar, then drizzle in vanilla
3. Increase to medium-high speed and whip to stiff peaks
4. Take the bowl off the mixer and use the whip attachment to mix in the contents from the bottom of the bowl (any remaining powdered sugar)
5. Serve immediately, or cover and refrigerate until use

1. Preheat oven to 200°
2. In a double-boiler over medium heat, combine egg whites and sugar and whisk constantly until smooth, about 10 minutes
3. Transfer the mixture to a mixer fitted with a whisk attachment. Whip on medium speed until stiff peaks form, and the meringue is glossy and not dry, about 10 minutes
4. Transfer meringue to a pastry bag fitted with a ½" round tip
5. Pipe into mushroom stems and tops onto sheet pan lined with parchment paper
6. Dip your finger in a bowl of water to smooth over the tips on the stems and caps. You can shape the caps to make bumpy or smooth using this same technique
7. Bake for 1½ hours, then turn oven off but leave oven door ajar and allow mushroom parts to remain in the oven for an additional hour
8. To assemble, stick a paring knife into the bottom of the caps and turn to create little holes to fit stems
9. Smear a bit of ganache or frosting into holes. Attach stems and place upright to display
10. Paint spots of ganache onto mushrooms, or dust with cinnamon or cocoa powder to finish

1. Place melted chocolate into food processor with tapioca maltodextrin
2. Pulse until combined and dry. Continue to process until mixture takes on a dirt-like texture. Add more tapioca maltodextrin if needed

1. Lift cake/parchment paper out of pan to a clean work surface. Spread whipped cream evenly over top using a metal offset spatula. Grab the long edge of the parchment paper with two hands and gently roll cake onto itself, pulling off paper as you roll. For tree stump, diagonally cut a 2" length from one end of cake and set aside
2. Using two long metal spatulas, carefully transfer log to a serving platter
3. "Glue" stump onto log with ganache. Spread remaining ganache on the log, dragging spatula along icing to simulate tree bark
4. Decorate with meringue mushrooms and dessert dirt. Dust with powdered sugar, and decorate log with fondant holly & berries if desired. Refrigerate until eating