This French cake known as a 'Buche de Noel' or to us a Yule Log is named so because the rolled cake actually does look like a yule log.
There are two separate amounts of cocoa and of sugar. The recipe is unclear as to which amount goes where. My cake broke on rolling and it stuck to the tea towel. I ended up putting it all in the freezer and mixing the cake and filling together to make a pretty good chocolate ice cream. - 14 Dec 2016
I made this for my daughter's French class Christmas fete. Yes it is alot of work but worth it. I followed other tips like beating the egg yolks a good 5 minutes, greasing the parchment paper very well and I put quite a bit of powdered sugar on the dish towel before rolling. I had enough of the mousse left over to decorate. Here's what I did and it was beautiful (will post a photo later). I cut one end of the log (about 4") at an angle. Frost the sides, top and bottom and use some mousse to "glue" on the stump (piece cut off earlier) then frost the stump as well except for the top. Next run fork tines across the log and upward on the stump so you have ridges like a log. Then dust with powdered sugar and decorate with holly or mistletoe or pine sprigs. I also made mushrooms from chocate truffles stuck onto a piece of broken candy cane rubbed with chocolate, and dipped in powdered sugar. - 20 Dec 2005 (Review from Allrecipes USA and Canada)
This cake received applause at our Christmas dinner. And, it should have. After all, my mother and I had to make it twice. Let me explain. You MUST BEAT the egg yolks and sugar until they are very pale. For all of you Texas Aggies out there, BTHO the egg yolks. Let the electric mixer run at the highest speed for at least 5 minutes. Because this cake contains no rising agents like baking powder or yeast, its "fluffy-ness" depends upon the amount of air that you "BEAT" into it - hence the stiff egg whites and the pulverized egg yolks. We decorated the cake with whipping cream and homemade mushrooms (hershey kisses and small marshmallows on toothpicks - with red gel polka dots). - 27 Dec 2004 (Review from Allrecipes USA and Canada)