Ok, I have to admit that I rolled this the wrong way (long side) and then tried to reconstruct it for my photo with so-so results. It still tasted delicious despite my mistake. This just goes to show you that even if you think you've really messed up a recipe, you can always salvage it.
Mix all ingredients in a large mixing bowl. Line a jelly roll pan that is approximately (9x13) with parchment paper or grease and flour well; spread mixture evenly in pan. Bake for 15 minutes. Press the center to make sure that the cake springs back and it done. Immediately turn out onto a linen kitchen towel which has been generously sprinkled with icing sugar. Remove parchment paper and sprinkle with more powdered sugar and roll up, beginning with the narrow end, in the linen towel; set aside until cool. Unroll, spread with filling, re-roll and sprinkle with more powdered sugar. Wrap with cling film and refrigerate.
Mix well with electric mixer until well blended. Refrigerate until ready to use.