Summer fruits such as strawberries, peaches and nectarines taste sumptuous with cream. Here, these aromatic fruits are combined with cream and yogurt to make a delicious filling for a light-as-air, fat-free sponge.
Use a 33×23cm Swiss roll tin. Grease and line with baking paper. Preheat oven to 200 degrees C.
Place eggs and sugar in a large bowl. Use an electric mixer and beat until very thick and pale and the mixture leaves a trail on the surface when beaters are lifted out. If using a hand whisk, set the bowl over a pan of almost boiling water, making sure that the water does not touch the base of the bowl.
Sift half the flour over the egg mixture and gently fold it in with a large metal spoon. Sift the remaining flour over the top and fold it in with the lukewarm water.
Pour mixture into the tin; give tin a gentle shake to spread the mixture evenly into the corners. Bake for 10–12 minutes or until the sponge is well risen, springs back when pressed gently with a finger and is pale gold in colour.
Turn out onto a sheet of baking paper slightly larger than the sponge. Peel off lining paper. Trim the crusty edges of the sponge with a sharp knife; make a score mark 2.5 cm from one of the short edges (this will make the sponge easier to roll up).
Roll up loosely from the short side, with the paper inside, and place seam-side down on a wire rack to cool.
When sponge is cold, carefully unroll it and remove the paper. Whip cream and vanilla essence until soft peaks form, then fold in the yogurt. Spread over the sponge, leaving a 1cm border all the way around. Scatter fruit over the cream. Carefully re-roll the sponge and place it seam-side down on a serving plate.
Put 2 1/2 cm wide strips of baking paper diagonally, at an equal distance apart, over the cake. Dust with the icing sugar to create a striped effect. Carefully remove the paper. Decorate with the extra fruit. Keep roll in the refrigerator until ready to serve. This sponge is best eaten within a day of making.