WHAT YOU NEED

For the rosemary cream

300ml (10½fl oz/generous 1¼ cups) double (heavy) cream
2 large sprigs of rosemary
60g (2¼oz) white chocolate, finely chopped

For the sponge

90g (3¼oz/⅔ cup) plain (all-purpose) flour
20g (¾oz/3 heaped Tbsp) cocoa powder, plus extra for dusting
½ tsp baking powder
4 eggs
100g (3½oz/½ cup) caster (granulated) sugar
finely grated zest of 1 orange
2 Tbsp chopped roasted hazelnuts

Start with the rosemary cream, as it needs time to chill. Heat the double cream with the rosemary in a small saucepan until steaming, just before the boil. Remove from the heat, cover and leave to steep for 15 minutes.

Add the chopped white chocolate to a heatproof bowl.

Remove the rosemary from the pan and gently reheat the cream until hot but not boiling. Pour the cream over the chocolate and stir gently until smooth. Cover and chill in the refrigerator for 2 hours, or until completely cold.

Preheat the oven to 180°C (160°C fan/350°F/gas mark 4). Line a 23 x 33-cm (9 x 13-in) Swiss roll (jelly roll) pan or baking sheet at least 1cm (½in) deep.

Sift together the flour, cocoa powder and baking powder and set aside.

Using an electric whisk or stand mixer, beat together the eggs, sugar and orange zest on high speed for 3–5 minutes until thick, pale and nearly tripled in volume. You want the eggs to get to ribbon stage – when you lift the beaters from the mixer, the eggs should fall back in thick trails and stay on the surface for a few moments before disappearing. Sift in the flour mixture in three batches. Gently fold after each addition, being really careful not to knock out too much air. Make sure you’re getting right down to the bottom of the bowl where pockets of flour may be hiding.

Once all the flour has been incorporated, pour the batter into the pan, again being careful not to knock out more air. Tilt the pan so the batter fills all the corners. Bake for 12–15 minutes until the cake feels springy to the touch.

Remove from the oven and let it cool for a minute. Place a sheet of baking paper that’s a little larger than your pan on your work surface. Dust generously with cocoa powder and then invert the sponge onto the paper. Peel off the baking paper that is now on top and, starting from a short end, slowly and tightly roll up the cake (with the bottom piece of baking paper rolled inside with it). Place the roll seam-side down and leave to cool completely.

Take the rosemary cream from the refrigerator and whisk until it thickens to stiff peaks.

Once cooled, carefully unroll the sponge. Don’t panic if you have any cracks! Spread the cream evenly onto the cake and sprinkle on the chopped hazelnuts. Re-roll the sponge in the same direction as before and place in the refrigerator to firm up.

When ready to serve, slice off each end to show the neat swirl and dust with a little more cocoa powder.