To make a Swiss roll, simply use the basic whisked sponge mixture but made with self-raising flour instead of plain to give a better volume. The thin flat cake is rolled and cooled around greaseproof paper so it keeps its characteristic shape. Preheat the oven to 220°C, 425°F, Gas Mark 7. Line a 30 × 23cm (12 × 9in) Swiss roll tin with greased greaseproof paper. Sift 125g (4oz) self-raising flour into a bowl.
Make the whisked sponge mixture as in steps 1 and 2. Pour into the prepared tin and spread level with a palette knife. Bake for 8–10 minutes until just firm to touch.
Sprinkle a large sheet of greaseproof paper with caster sugar. Turn out the cake on to the sugary paper, peel off the lining paper and trim the edges. Roll up with the sugar paper inside. Cool.
Unroll, and spread with 2tablespoons jam to about 2.5 cm (1 in) from the edge, then 125g (4oz) buttercream.
Reroll the cake and discard the sugar paper. Dust with icing sugar through a small, fine sieve, then serve cut into thick slices.