Rhubarb marshmallow Ingredients 20cm square cake tin clingfilm a dash of vegetable oil for the rhubarb purèe: 300g rhubarb, chopped 50g caster sugar 1tbsp water for the syrup: 450g caster sugar 200ml water 1tbsp glucose syrup (available from supermarkets) for the mallow: 9 leaves gelatine a little water 140g thick rhubarb puree 2 large egg