The Great British Bake Off sees passionate home bakers take part in an elimination competition to test every aspect of their baking skills. Each week the surviving bakers are put through three challenges in a particular baking discipline, such as cake, pastry, pies, bread, or biscuits. Round One is the Signature Challenge, which contestants will have had a chance to practice. However Round Two, the Technical Challenge, is unknown to them until filming, and they are given identical ingredients and a vague recipe to follow. Finally, the Showstopper Round tests their ability to impress the judges with outstanding workmanship, decoration, and design. Judging the baking are professional baker Paul Hollywood and food writer Mary Berry, who was replaced by restaurateur Prue Leith after the show's move from the BBC to Channel 4.