METHOD

1. Place the cream, yoghurt, icing sugar and vanilla in a large jug and whisk until the sugar is dissolved. 
2. Pour the mixture into a 20 x 30cm metal slice tin and freeze for 2½ hours or until firm and just frozen.  
3. While the ice-cream mixture is freezing, place the caster sugar, blackberries and lemon juice in a small saucepan over high heat. Cook, stirring occasionally, for 10 minutes or until syrupy. Refrigerate until cold. 
4. Remove from the freezer and, using a butter knife, break up the mixture into small pieces. Place the mixture in a food processor and process for 2–3 minutes or until just smooth, breaking up any large pieces with a spoon. 
5. Spoon into a 2-litre-capacity loaf tin. Spoon over half the chilled blackberry mixture and swirl through, using a knife. Repeat with the remaining ice-cream mixture and blackberry mixture. Freeze for 2 hours or until firm. Scoop into bowls or cones to serve. Makes 1.7 litres