This recipe includes a banana in the filling but you can fill this rolled up sponge with jam, peanut butter or mashed banana.
Ingredients
2 eggs
50 g caster sugar
50 g self raising flour
40g jam
1 banana, mashed
Sugar for dusting
Method
- Preheat the oven to 200 °C/ Gas 6.
- Line a Swiss roll tin 20 x 30 cm with baking parchment paper.
- Whisk the eggs and sugar for about 10 minutes until the mixture is thick and creamy and you can leave a trail in the mixture. This forms a foam.
- Sieve in the flour and fold in gently with a metal spoon – figure of eight shape.
- Spoon into the tin and bake for 8-10 minutes until lightly browned and the cake springs back to touch.
- Turn onto a sugared greaseproof paper which is on top of a tea towel. Trim the edges to help with rolling up.
- Spread with warm jam and mashed banana and roll from the short side. Hold in place until firm and sprinkle with a bit more sugar to serve.
The science bit
Eggs and sugar whisk to a foam. Albumen is the protein in the egg and this extends and traps the air bubbles.
On heating the air expands and pushes up the egg, sugar and flour mixture.
Flour contains gluten which is a protein which sets when heated.
The egg protein denatures, coagulates and sets with the gluten and forms the sponge structure.
The cake changes colour as the starch changes to dextrin and the Maillard reaction takes place.
The lemon juice protects the banana from changing colour due to enzymic browning.
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