A little autumn sunshine in a jar, with an unexpected Somerset twist ... Sometimes the best kitchen experiments start with an ingredient that makes you stop and wonder what on earth you're going to do with it ... Enter the mangelwurzel. Traditionally grown as a fodder crop, this rather magnificent root vegetable has been keeping me busy in the kitchen, finding its way into everything from brownies and truffles to savoury bakes and, now, a rather lovely little preserve. This