Prepare a silicone 12 x 16 inch (30 x 40 cm) non-spill baking sheet or a large baking tray lined with parchment paper.

To make a chocolate sponge cake, preheat the oven to 390°F (200°C). Mix cake flour with cocoa powder by sifting them in a large bowl and set aside.

Pour milk and add butter into a small bowl. Place the bowl over a larger container filled with hot water and let the liquids reach the temperature of 122-150°F (50-60°C) by using a cooking thermometer to check.

Place whole eggs, vanilla, and granulated sugar in a heat-proof bowl or the bowl of a stand mixer and beat a few times with a hand whisk.

Bring the bowl over a bain-marie or water bath and beat with a hand whisk until it reaches a warm 104°F (40°C).

Remove the bowl from the water bath, and whip the mixture until perfection in just 6-7 minutes using an electric or stand mixer with a whisk attachment.

Reduce the mixer speed once the batter triples in volume, turns whitish, and flows like a thick ribbon from the beaters. Whisk at the lowest speed for 2 minutes to adjust the batter's texture.

Sift the flour mixture over the bowl with batter and gently mix with a silicone spatula. Start from the bottom, work your way up, and give the container a gentle counterclockwise turn.

Take two tablespoons of batter and combine it with warm milk and butter in a bowl. Use a spatula to mix everything together.

Return the mixture to the main preparation and mix it thoroughly, starting from the bottom and moving upwards.

Pour the cake batter into the silicone baking sheet from 8 inches (20 cm) above the pan to remove large air bubbles. Alternatively, spread the batter onto a large baking sheet lined with parchment paper. Make a 12 x 16 inches (30 x 40 cm) rectangle with 1/2 inch (1 cm) thickness.

Use a bent spatula or a dough scraper to smooth the surface, but don't overdo it in the same area.

Bring the baking pan to the oven and immediately lower the oven temperature from 390°F (200°C) to 375°F (190°C). Bake for 10-12 minutes. Don't overbake the cake. Check for doneness with a toothpick: it should come out dry.

Remove the sponge cake from the oven, and while it is hot, flip it on a clean tea towel dusted generously with icing (powdered) sugar.

Carefully peel off the silicone baking sheet or parchment paper. With a long serrated knife, trim the cake edges on all sides, aiming for the thinnest edge possible. Cover the cake with a fresh piece of parchment paper.

Roll the cake with parchment paper inside and towel outside, and let it cool for just 10 minutes. Then, unroll it and allow the cake to cool at room temperature for approximately 15-20 minutes.

To make the sweetened whipped cream, place all the cream ingredients in a cold mixing bowl and beat with an electric mixer until firm.

To roll the cake, remove the parchment from the top of the cake. Cut it into four parts horizontally (along the cake's long edge) to obtain four 7 x 37 cm cake sponges.

Keep the strips close to each other. Spread the cream in an even layer over four cake strips using an offset spatula.

Start rolling the first strip with your hands, making a tight cake roll's core. Continue rolling and tighten the roll as you go.

Connect the short side of the roll with the short side of the second sponge strip and roll. Firmly roll the cake, preventing the rolled cake and cream from protruding to one side.

Carefully flip the cake roll upright, placing it on a cake board or a serving platter. The spiral ends will become exposed at the top.

Take the third cake layer, join it where the second strip is finished, and continue to roll. Tight it and finish rolling the log cake with the fourth cake layer.

To get a tidy vertical cake, use an acetate cake collar to cover the cake sides. Then, wrap the cake with a mousse ring to keep it in place. Adjust the ring for a secure fit. Alternatively, simply cover the sides and the top of the rolled cake with plastic film to prevent it from drying. Refrigerate the cake for at least 3-4 hours or overnight. 

To decorate the tree stump cake, first, make chocolate ganache with butter. Chop a dark chocolate bar or use chocolate callets. Alternatively, you can use a food processor to crush the chocolate.

Place chopped chocolate in a small saucepan and bring it over a water bath. Melt chocolate, stirring with a wooden spoon. Allow the melted chocolate to cool to room temperature, stirring occasionally.

Add softened butter, cut into medium-sized cubes, and whip with an electric mixer until creamy and homogeneous.

Take the rolled cake from the refrigerator, place it on a turntable, peel off the plastic wrap, or remove the cake ring and acetate collar. Spread the chocolate ganache on top of the cake.

With a small offset spatula, create a swirl while spinning the cake. Alternatively, use a fork or a toothpick to make lines resembling the rings of the tree.

Use a rubber spatula to evenly coat the sides of the cake, working from the bottom to the top. Try to mimic the bark of the tree, making it slightly higher than the tree rings. Use a small offset spatula or a fork to draw the vertical lines around the cake to represent the bark of the tree.

Decorate the top and sides of the tree stump cake with meringue mushrooms, chopped pistachios, sugared cranberries, edible moss, rosemary sprigs, etc. Dust the cake with icing sugar or shredded coconut to give the effect of snow, and serve right away.