The cookbook, "Ratio", is unlike any other cookbook Anna and Kristina have ever tested, and is really more than a cookbook. Although recipes are included, what it does provide are basic ratios that one can use to develop one's own variations on recipes. For example, if one knows the ratio of fat to flour to sugar in a cookie recipe, that ratio knowledge can be the basis for so many other cookies. As such, in the three hours they have on cook day, they will be preparing three recipes directly from the book (chicken sausages with basil and roasted peppers, lemon tart, and sponge cake with basic ganache) and three additional recipes based on the ratios provided of the previous three dishes (duck sausages with apples and chestnuts, spinach, panchetta and garlic tart, and coffee & walnut sponge cake). Their guest taster is David Robertson an executive chef and cooking instructor, who knows his cooking ratios. Anna and Kristina know that Chef David will further critique them on presentation as he is also a food stylist, which may be a little intimidating as the book contains few photographs of the finished products as the ratios have no preconceived end product. Anna and Kristina will have to wade through what reads like a textbook to impress Chef David, who suggests treating additional ingredients as one often treats salt: to taste. Anna and Kristina also have issue with techniques and knowing appropriate flavor combinations. In addition, they taste test different types of fat to use in cookies, which they will translate into the making of their tart crusts. And they discuss measuring tools essential in the kitchen.