Lemon and blackcurrant stripe cake

We had a momentary wobble as the recipes for SWEET were coming together that there was not enough colour. Yotam ran off to his local grocer to get as many bright berries as he could, and the refrain of the week was: colour, colour, colour! This tall, conical showstopper of a cake is one of the happy outcomes. It starts its life, simply, as a flat sponge cake in a baking sheet. Rolled up and covered in silky buttercream, it looks rather like a barrel. Cut into it, however – revealing the stripes! – and it looks like a whole lot of vertically inclined (and very colourful) fun.

Serves 8–10 (It’s not a wide cake – just 14cm – but it’s high) 8 large eggs, whites and yolks separated ⅔ cup plus 2 tbsp/140g granulated sugar, plus 1 ½ tbsp 1 tbsp lemon juice, plus finely grated zest of 1 small lemon (¾ tsp) ½ cup plus 1 tbsp/80g all-purpose flour

⅛ tsp salt Confectioners’ sugar, for dusting BLACKCURRANT (OR MIXED BERRY) PURÉE 300g blackcurrants (or mixed berries), fresh or frozen and defrosted, plus 40g to garnish ¼ cup/50g granulated sugar BLACKCURRANT (OR MIXED BERRY) BUTTERCREAM ¼ cup/85g light corn syrup (or golden syrup) ½ cup plus 1 tbsp/120g granulated sugar Scraped seeds of ½ vanilla pod 4 large egg yolks 1 ¼ cups plus 1 tbsp/300g unsalted butter, cut into 3cm cubes, softened ½ cup/100g blackcurrant (or mixed berry pureé) The buttercream can be made up to 3 days in advance and stored in the fridge or freezer. Just bring it back to room temperature and quickly whip it in the electric mixer to restore its fluffiness before spreading. Although the cake is best eaten on the day it’s made, any leftovers will be fine the following day if stored in the fridge. As always, bring it back to room temperature before serving.

Preheat the oven to 200°C. Line a shallow rimmed baking sheet (approximately 38 x 30 cm) with parchment paper and set aside.

Place the egg yolks in the bowl of an electric mixer with the whisk attachment in place. Add the ⅔ cup plus 2 tbsp/140g granulated sugar and the lemon juice and beat on mediumhigh speed for about 3 minutes, until pale and thick. Transfer the mixture to a large mixing bowl and sift the flour and salt directly over the egg mixture in two batches, folding through the mixture with a rubber spatula after each addition. Sprinkle the lemon zest on top and set aside.

Place the egg whites in a clean bowl of an electric mixer with the whisk attachment in place. Whisk on medium-high speed until soft peaks form, then slowly pour in the 1 ½ tbsp granulated sugar. Continue to whisk until firm peaks form, then gently fold a third of the egg whites into the egg yolk mixture until incorporated. Finally, fold in the remaining egg whites until combined, then scrape the

mixture into the lined baking sheet. Even out with a small spatula and bake for 15 minutes, or until light golden brown and a toothpick inserted into the centre comes out clean.

Remove from the oven and place on a wire rack to cool in the pan for 5 minutes before dusting the top lightly with confectioners’ sugar. Place a clean kitchen towel on top of the sponge cake and then flip it over so that it is now lying on top of the kitchen towel. Carefully peel away the paper and trim the very edges of the sponge. Be careful not to cut away too much; you really just want to straighten out the edges. Starting at the shorter edge of the cake, carefully roll it up (along with the kitchen towel). This is to “train” the cake, ready for rolling up again later. After about 20 minutes, or when no longer warm, unroll the cake. With the short end facing you, measure and cut three equal strips parallel to the long edge, each about 4 inches/10 cm wide. (If you have a pizza cutter, this is a really easy way to cut the strips.) Cover with a clean kitchen towel and set aside.

To make the purée, place the blackcurrants (or berries) and granulated sugar in a medium saucepan and place over medium-low heat. Warm through for 4–5 minutes, until the blackcurrants (or berries) have softened and the sugar has dissolved. Transfer to a food processor and process to form a purée. Strain through a fine-mesh sieve set over a bowl to catch the purée; you need ⅔ cup/150g, so save any extra in the fridge to spoon over yogurt.

To make the buttercream, place the corn syrup (or golden syrup), granulated sugar and vanilla seeds in a medium saucepan. Place over low heat and stir until all the sugar dissolves; this is your sugar syrup.

While the syrup is cooking, place the egg yolks in the bowl of an electric mixer with the whisk attachment in place. Beat on medium-high speed until thick and pale yellow in colour. Leave the machine on while you check the sugar syrup; when all the sugar has melted, stir again, increase the heat to medium and simmer until bubbles begin to appear. Swirl the pan gently and continue to simmer until there are large bubbles all over the surface of the syrup.

Remove the pan from the heat and carefully pour the hot syrup in a slow, steady stream down the edge of the mixing bowl into the beating yolks. When all the syrup has been added, increase the mixer speed to high and continue to beat the mixture for about 10 minutes, until the outside of the bowl is no longer warm. Gradually add the butter, one cube at a time, allowing it to be incorporated into the mixture before adding the next. When all the butter has been added, scrape down the bowl and continue to beat for another minute, until the buttercream is very smooth and light.

Add a scant ½ cup/100g of the blackcurrant (or mixed berry) purée and beat on medium speed until fully incorporated.

Spread each of the strips of sponge with about 85g of the buttercream; this should leave about 300g to frost the top and sides of the cake. Take one strip of sponge and, starting with the short end, roll it up. Once this strip is rolled, position the exposed end at the beginning of the next strip and keep rolling. Again, once this is rolled – the cylinder will be getting wider now – position the exposed end at the beginning of the last strip and continue to roll. You now have a rolled cylindrical cake! (Imagine, for a moment, if you lined up the three strips end to end to create one very long strip. Then imagine rolling that very long strip up, from one end to the other. You should end up with a coiled barrel shape.) Turn the cylinder onto the serving plate so that it is standing on one of its flat ends.

Spread the remaining buttercream all over the top and sides of the cake, smoothing with a spatula to create an even surface. Dribble the remaining ¼ cup/50g blackcurrant purée on top of the cake and top this with the blackcurrants (or berries) reserved for garnish. Set aside for 1 hour at room temperature (or in the fridge if it is a very warm day) before serving.