Preheat oven to 220⁰C Mark 7. Line a 33.6cm x 22.5cm Swiss roll tin.
Put the eggs and the 100g of sugar into a bowl and whisk until very light and creamy. The mixture should be stiff enough to retain the impression of the whisk for a few for a few seconds.
Gently fold half the flour into the whisked mixture using a metal spoon.
Fold in the remaining flour, making sure it has all been incorporated and there are no lumps. Stir in the hot water.
Pour the mixture into the prepared tin, smoothing it over evenly and gently. Bake in the oven for 7 – 9 minutes until well risen, golden brown and spongy.
Meanwhile, have ready a sheet of greaseproof or baking parchment and sprinkle on some caster sugar. To make the sponge pliable you can place the paper over a damp tea towel.
Turn out the cake quickly onto the paper and trim away the edges.
Place a second sheet of paper on top of the sponge and roll it up loosely using the sugared paper underneath as a guide. Leave to cool completely on a cooling rack, covered in the paper.
To make the filling:
Put the butter or margarine into a bowl, sift the icing sugar and add it gradually with a little milk creaming everything together well until very smooth.
When the sponge is completely cold gently unroll it and remove the paper. Carefully spread the sponge with the cream filling, then reroll.
