200g dark chocolate, melted and cooled slightly, plus extra for topping
STEP 1Line a 900g loaf tin (ours was 9 x 20 x 7cm) with two sheets of overlapping baking parchment, leaving some overhanging on all sides of the tin. Put 175g of the raspberries, the caster sugar and lemon juice in a pan over a medium heat and simmer for 3 mins until softened slightly. Tip into a food processor or use a hand blender to blitz until smooth.
STEP 2Whisk the double cream, vanilla and condensed milk using an electric whisk until soft peaks form. Pour in the raspberry purée, then stir carefully a few times to marble the raspberry through the cream.
STEP 3Tip the remaining raspberries into the base of the lined tin. Cover with a third of the cream mixture, spreading it out evenly. Tap the tin down on a surface so that the mixture covers the raspberries. Using a spoon, drizzle over half of the melted chocolate to cover the cream. Top with another third of the cream mixture and spread it out. Drizzle over the remaining chocolate and top with the remaining cream.
STEP 4Use the overhanging parchment to cover the top of the tin, using more parchment if it doesn’t cover the terrine completely, and freeze for at least 8 hrs, or overnight. Before serving, let the ice cream sit at room temperature for 10 mins. Tip upside down and remove from the tin, and drizzle with a little more melted chocolate to decorate. Run boiling water over your knife, wipe dry, and slice to serve.