Just as it feels like winter has been dragging on too long, fluorescent sticks of shocking pink rhubarb begin to appear in the greengrocer. Their arrival always feels like a turning point, some brightness in amongst the still short days and a promise of spring to come. That said, spring is still a fair way off so today we’re roasting that rhubarb – plus a handful of frozen blueberries – beneath a crunchy, buttery crumble for the ultimate in winter comfort puddings.