Gregg Wallace visits a croissant factory in France that produces 336,000 pastries a day, and discovers how an 83-year-old strain of yeast is used to create the perfect flavour. Cherry Healey talks to a professor who specialises in exploring human senses about the perfect way to eat a croissant and visits a farm that produces concentrated butter that is 99.8 percent fat. Plus, Ruth Goodman is in Paris investigating the croissant's surprising Austrian origins and the role of bread in the French revolution