Picking produce at its prime ensures every mouthful is worthwhile. In this second excerpt from her new cookbook, our columnist shares ideas for vibrant autumnal platefuls: chocolate rye porridge with quick honey pears, bao with sweet potato and pickled cucumber, not-chicken soup, gentle potato chowder with toasted chilli oil, beetroot, rhubarb and potato gratin, bay and lemon-laced creme caramel, salted chocolate truffles, malt loaf with prunes and black tea.