Preparation:
You will also need a shallow, 11 x 7-inch baking tin, a large, shallow baking dish, and a 3.5 pint (2 litre) polythene freezer box 8 x 8 inches x 2.5 inches deep (20 x 20cm x 6cm deep).
Pre-heat the oven to gas mark 5, 375F (190C).
First of all make the crumble by combining all the ingredients together in a bowl and using your hands to rub the butter into the flour so that the mixture comes together to form small, pea-sized balls of dough (rather as if someone had made a half-hearted attempt to make breadcrumbs from very fresh bread!). Now sprinkle this evenly into the baking tin and leave on one side.
Now cut the rhubarb into half-inch (1cm) lengths and place them in a large, shallow baking dish along with the sugar and the lemon juice. Place the dish on a lower shelf in the pre-heated oven and the tin containing the crumble mixture on the shelf above. The crumble needs to be baked for 10 minutes, then remove it from the oven and leave to cool. The rhubarb may need a further 15-20 minutes' cooking before it is completely tender: when it's cooked, take it out and leave it to cool a little before pouring it into a food processor or blender. Process until you have a smooth puree, then pour it into a measuring jug, cover, and transfer to the fridge to chill.
Before making the ice cream, use your hands to break up the cooled crumble and restore it to small, pea-sized pieces (if they're too big, the pieces are unwieldy to eat in the ice cream; if they're too small, they disappear). Next stir the cream into the rhubarb puree, pour into an ice-cream maker and churn until the mixture has the consistency of softly whipped cream. Quickly spoon it into the polythene freezer box and stir in the crumble pieces. Put the lid on, then freeze for a minimum of 2 hours or until the ice cream is firm enough to serve.
To make without an ice-cream maker, freeze the mixture (without the crumble) in the box for 3-4 hours, then whisk and return to the freezer. Re-freeze for a further 2 hours then whisk again and stir in the crumble before the final freezing.
If frozen solid, the ice cream will need to be transferred to the fridge for about 25 minutes before serving, to allow it to become soft enough t |