In a large bowl sift together the flour, 3 tablespoons of cocoa powder, and baking powder.
Next, add in the sugar, vanilla, eggs, and oil and vigorously whisk together until smooth and combined.
Transfer the mixture to a 13x18 cookie sheet tray that has been lined with parchment paper and spread the batter out evenly using an offset spatula.
Bake at 350° for 15-17 minutes and the invert the cake onto a large clean kitchen towel that’s been dusted with ¼ cup of cocoa powder. Be sure to remove the parchment paper.
Roll the cake up in the towel and let it completely cool to room temperature, which takes about 2 to 2 ½ hours.
In the meantime, make the filling by whisking together the whipped cream, sugar, vanilla, and cocoa powder until medium-stiff peaks have formed.
Next, add in the mascarpone cheese and whisk until stiff peaks have formed. Set in the refrigerator to keep cool until ready to use it.
Now, prepare the ganache, and optional sugared cranberries and rosemary, as well as meringue mushrooms.
Once the cake is completely cooled, gently unroll it, and then evenly spread the mascarpone whipped cream all over the enter from edge to edge.
Roll the cake up tightly and make sure the filling is not coming out of the edges.
Roll the cake up tightly in plastic wrap and chill it for about 30 minutes in the refrigerator to help restabilize the shape and filling.
Slice the cake towards the top at an angle and then attach is to the side of the cake using some ganache or leftover whipped cream filling.
Spread the ganache all over the top of the and sides of the yule log leaving the cut ends opened.
Take a fork and run streaks down the sides and top of the cake.
Make-Ahead: You can make this yule log up to 1 day ahead of time. Be sure to keep gently covered in the refrigerator and then take it out 1 hour before ready to serve.How to Store: Cover and keep in the refrigerator for up to 3 days. You can cover and freeze this for up to 3 months. Slice and eat it right from the freezer or thaw it in the refrigerator for 1 day before serving.It is ok if there are some cracks in the roll cake because the entire thing will be covered in chocolate.When using the fork to create the bark-like visual, do not press too deep you want to make sure you are only staying in the ganache.After you’ve rolled the cake up with the filling, you can let it sit in the refrigerator for up to 2 days before adding on the ganache.The eggs do not need to be at room temperature.Feel free to substitute out the macadamia nuts for hazelnuts or even pecans.If you want to hyper-chill the cake after rolling it with the filling, place it in the freezer for about 15-20 minutes.