Follow these detailed steps to create your Traditional Chocolate Yule Log successfully:

1. Preheat the Oven: Start by preheating your oven to 350°F (175°C). Prepare a 15×10-inch jelly roll pan by lining it with parchment paper and lightly greasing it.

2. Prepare Sponge Cake Batter: In a large bowl, beat the eggs and granulated sugar with an electric mixer on high speed until the mixture is thick and pale (about 5-7 minutes).

3. Combine Dry Ingredients: In a separate bowl, sift together the cocoa powder, flour, baking powder, and salt. Gently fold the dry ingredients into the egg mixture until just combined.

4. Add Vanilla: Pour in the vanilla extract and fold it gently into the batter. Be careful not to deflate the mixture.

5. Spread the Batter: Pour the batter into the prepared pan, spreading it evenly with a spatula.

6. Bake the Cake: Place in the preheated oven and bake for 12-15 minutes. The cake should spring back when lightly touched.

7. Cool the Cake: Remove the cake from the oven and allow it to cool for about 5 minutes. While it’s still warm, invert the cake onto a clean kitchen towel sprinkled with powdered sugar. Carefully peel away the parchment paper.

8. Roll the Cake: Starting from one short end, roll the cake with the towel inside. Let it cool completely rolled up (about 30 minutes).

9. Make the Filling and Frosting: While the cake cools, prepare the filling. In a small saucepan over low heat, melt the chopped chocolate and butter together, stirring until smooth. Remove from heat and allow it to cool slightly.

10. Whip Cream: In a separate bowl, whip the heavy cream, powdered sugar, and vanilla until soft peaks form.

11. Combine Filling: Fold the whipped cream into the cooled chocolate mixture gently until well incorporated.

12. Unroll the Cake: Carefully unroll the cooled cake. Spread the filling evenly over the surface, leaving a slight margin on the edges.

13. Re-Roll the Cake: Carefully roll the cake back up without the towel this time. Transfer to a serving platter seam-side down.

14. Frost the Yule Log: Spread the remaining chocolate filling over the entire log using a spatula.

15. Decorate: Dust with cocoa powder for a rustic look. Optionally, embellish with fresh berries or edible decorations, like chocolate shavings or meringue mushrooms.