Arrange the rhubarb batons in a single layer in a heavy-based pan
Sprinkle over the sugar and pour over the water
Place over medium heat and bring gently to a simmer
Once simmering, cook for a further 8–12 minutes until just tender but still holding their shape
Remove from the heat and allow to cool in the syrup
In a large bowl, beat the double cream and condensed milk together until the mixture resembles whipped cream
Add the ground cardamom and stir until combined
Once the rhubarb is cooled, add all but a few pieces to a blender and blitz until smooth
Reserve a few pieces for garnish
Stir the blended rhubarb through the ice cream base
Transfer to a container, cover with a lid and freeze
Remove from the freezer about 15 minutes before serving to allow it to soften slightly
Top each serving with a piece of rhubarb to finish
