Preheat the oven to 350 degrees F. and grease or butter a jelly roll pan or a rimmed baking sheet (I used a 12 x 16 inch pan). Then, line the pan with parchment paper and spray the parchment.
In a large bowl, whisk the 4 egg yolks, half of the honey, and the vanilla until it becomes lighter in color and a little bit thicker.
In a separate bowl, beat the egg whites and the remaining honey until stiff peaks form.
Sift the flour, cocoa powder, baking powder, and salt over top of the bowl with the egg yolks. Add the bran from the flour back in. Fold the egg yolks into the flour mixture until completely combined.
Then, add the egg whites to the bowl. Use a mixer to beat the egg whites into the batter on low speed, just until combined. You do not want to deflate the egg whites.
Evenly spread the batter onto the prepared pan and bake for 10 minutes. Allow the pan to cool for 10 minutes.
Spread out a tea towel and sprinkle it with powdered sugar.
Flip the cake onto the tea towel and slowly peel back the parchment paper. Roll the cake up in the tea towel - into a log shape.
Prepare the filling by whipping all of the ingredients together until soft peaks form.
Unroll the log in the tea towel and evenly spread the filling on it. Roll the log up tightly, wrap in plastic wrap, and chill for 1 hour.
Prepare the chocolate icing by beating the butter until fluffy. Add the remaining ingredients and beat until fluffy.
Spread the chocolate icing over top of the log and down the sides. Use a fork to scrape across the icing to make it look like tree bark and dust with powdered sugar.