1. Make the jam

    Cook 300g blackberries along with 2 tbsp lemon juice and 1 tbsp water in a pan over a low heat for 10 mins. Stir in 300g granulated sugar until dissolved. Bring to the boil and bubble rapidly, without stirring, for 15 mins, then put in a bowl, cover with clingfilm and leave to cool. Chill for at least 3 hrs.

  2. Prepare the pattern mix

    Beat together 20g caster sugar, 20g butter, 30g plain flour, 1 egg white and 10g of pink food colouring gel. Spoon into a piping bag fitted with a 2mm nozzle and set aside. Lightly grease and line a 22x32cm swiss roll tin with nonstick baking paper, so it fits snugly in the corners. Preheat the oven to gas 6, 200°C, fan 180°C. 

  3. Make the Swiss roll sponge

    Beat 4 eggs and 120g caster sugar in a large bowl using an electric whisk set to high for 10 mins, or until thick and very foamy. When held above the bowl, the mixture should take 8-10 secs to drop from a whisk. Use a metal spoon to gently fold in the flour and zest.

  4. Bake the patterns

    Pipe thin swirls and dots of the pattern mixture into the lined tin. Bake for 1 min to set slightly, then spread the sponge mix on top and smooth to level. Bake for 12 mins, until pale golden and springy. Meanwhile, cut 2 sheets of baking paper slightly larger than the tin. Put 1 on a large board.

  5. Get ready to roll

    As soon as the sponge is out of the oven, put the paper and board on top and flip to remove from the tin. Gently peel off and discard the lining. Put the second paper sheet on top and flip again. Remove the top piece of baking paper. Using a serrated knife, score a line 2cm from a shorter edge, then roll up with the paper, from this end. Cool for 2 hrs.

  6. Fill with jam and cream

    When ready to serve, carefully and slowly unroll the sponge as much as possible and remove the paper. Spread the jam over, followed by 15ml double cream, whipped to soft peaks, leaving a slight border of sponge around the edges. Roll up and transfer to a serving plate with the seam on the bottom. Eat within 2 days.

    RFO HERO 636x418 MasterclassStep6Calories 467 (23%), sugar 63g (70%), fat 17g (24%), saturates 9g (45%), salt 0.2g (3%), based on 8 servings.

  7. Ingredients

    Love the sound of this blackberry lace swiss roll? Why not try it yourself? Take a screenshot of the ingredients below to take to the supermarket.

    2 x 300g packs blackberries

    2 tbsp lemon juice

    300g granulated sugar

    150ml double cream, whipped to soft peaks

    For the pattern
    20g caster sugar

    20g butter, plus extra for greasing

    30g plain flour

    1 egg white

    1 x 10g tube pink or violet gel food colour

    For the sponge
    4 eggs

    120g caster sugar

    120g plain flour

    1 lemon, zested