Ingredients

• 1. Step 1

     Preheat oven to 190°C (170°C fan) mark 5. To make crumble, rub butter into flour in a medium bowl with your fingers until mixture resembles breadcrumbs. Mix in sugar. Squeeze crumble together into large clumps and scatter on a baking sheet (close together). Set aside.   
     

  2. Step 2

     Wash rhubarb and shake off excess water. Tip wet rhubarb into a roasting tin, mix in sugar and cover with foil.  Put crumble and rhubarb into oven; bake crumble for about 15min until golden and rhubarb for 20-25min until soft and tender. Set crumble aside to cool. Tip rhubarb into a blender or food processor and whiz to a purée. Pour into a jug, set aside to cool.  

  3. Step 3

     Break cooled crumble into rough 1.5cm pieces. In a large bowl, whisk cream, condensed milk and vanilla seeds until just holding soft peaks.  

  4. Step 4

     Whisk all but 3tbsp of cooled rhubarb purée into cream mixture and fold through 1/3 of crumble. Scrape into a 20.5cm square tin. Drizzle over remaining rhubarb purée and marble with a skewer or knife. Scatter over remaining crumble pieces. Cover with clingfilm and freeze until solid.  

  5. Step 5

     To serve, allow to soften at room temperature for 15min before scooping into balls.