Jam Swiss Roll

1. Preheat the oven to 200°C/fan180°C/gas 6. Lightly brush the base of a 33cm x 23cm Swiss roll tin with vegetable oil. Cut a sheet of greaseproof paper to fit the base of the tin exactly. Brush the paper with a little more oil, then dust with caster sugar and flour.

Tip
The eggs (which should be at room temperature) and caster sugar must be whisked for a full 10 minutes with an electric whisk, until pale and thick. It's thick enough when it's about three times the volume. When you lift out the whisk, the thick mixture that drips off should leave a trail on top of the rest.
2. Put the sugar and eggs into a large bowl that's resting on a tea towel and whisk with an electric hand whisk for 10 minutes, until pale and thick enough for the mixture to leave a trail when the whisk is lifted.

3. Sift half the flour into the mixture and fold in very carefully until no traces of flour are left. Repeat with the remaining flour. It's important to take your time and do it gently. Fold in 1 tablespoon lukewarm water.

4. Pour the mixture into the prepared tin and use a spatula to smooth it evenly into the corners. Bake in the centre of the oven for 10-12 minutes, until golden and risen and just firm to the touch. Meanwhile, put the jam in a bowl and stir well to loosen.

5. Lay out a damp clean cloth on the work surface. Lay a piece of greaseproof paper that is larger than the sponge on top. Dust the greaseproof paper with caster sugar. Run a knife around the edge of the warm sponge and turn out on to the sugar-dusted paper. Peel the paper off the base of the sponge. Trim off the edges of the sponge. Spoon the jam onto the sponge and spread out, leaving a little border of clean sponge all around. Make an incision about 1cm in from the short edge near you, being careful not to cut through the cake: this makes it easier to roll up.

6. Start rolling, using the incision to help you make the first turn. Use the paper to help you roll the sponge tightly. Sit it seam-side down until cold.