Prepare your swiss roll tin by greasing it and then placing baking paper onto it. Make sure it fits really well as you want the full shape of the tin.
Preheat your oven to 180C Fan.
Using an electric hand whisk, whisk together your sugar and eggs until light and a little frothy. It should only take a few minutes.
Sift in your gluten free flour, xanthan gum and cocoa powder (always sift cocoa powder otherwise it can be quite lumpy). Fold this into your mixture carefully until fully combined.
Pour/spoon the mixture into your tin, ensuring it spreads right to the edges.
Bake in the oven for just under 10 minutes. The sponge should have come away a little bit from the sides of the tin and be slightly risen.
Remove the sponge from the oven and very carefully invert it (turn it upside down!) onto another piece of baking paper on a flat surface. Carefully peel off the baking paper that was on the bottom of it in the oven.
Cut off a tiny slither of each edge to make them all straight and even and lightly score a line along the longest side (about an inch in). Now, whilst the sponge is still warm, roll the sponge up with the paper inside it as you roll. Put your rolled up sponge to one side and leave it to cool completely.
Whilst your sponge cools, make your icing for the inside and out. Add all your ingredients to a standing mixer (I use my KitchenAid) and sift in the icing sugar and cocoa powder.
Start the mixer on low and then increase to a higher speed as it all comes together. If it's not coming together, add a little extra dairy free milk very slowly.
It should be lovely and thick but still able to be spread. If you want it to be thinner, then add a little milk, and if you want it more thick then sift in some extra icing sugar (mine is always perfect or a little too thick, never too runny).
Now to put the Yule Log together. Carefully unroll and remove the baking paper. Fortunately I never find my sponge cracks using my recipe, but if it does, it doesn't matter - it will all be covered in icing!
Spread about a third of your icing on the unrolled sponge (I leave about a half cm gap around the edge). Carefully roll the sponge back up and transfer it to the serving board.
Cover the rolled up sponge with the remaining icing and use a fork to go over it to make a wood like pattern. Dust with icing sugar and to finish you can add a holly decoration - I make mine by using some red and green fondant icing.
Enjoy!