Create cake batter according to recipe. Pour batter (batter is very runny) into prepared pan and evenly spread the batter to all four corners.
Bake for 10 minutes and then let cool for 5 minutes. Then use a small knife to loosen the edges of the cake. – Using the parchment under the cake roll the cake up from the long side, not the short side.
Place rolled up cake, seam side down, onto a cooling rack and cool completely. Make frosting & then unroll cake.
Unroll cake and then spread frosting. Leave 1/2 border without frosting. Roll cake back up without the parchment paper. Chill completely, about 1-2 hours before decorating.
Prepare ganache and candy mushrooms for decorating. Once filled cake is chilled place rolled cake onto a platter. Use a serrated knife to cut one inch off each end of the rolled cake to give a nice crisp look to each end.
Cut log and position before spreading ganache, being sure to make a log look. Add decorations to log and set to chill.
To serve, arrange mushrooms around the Buche De Noel. Sprinkle with powdered sugar to make it look like snow. Serve cold or at room temperature.