Provided is a method for determining a performance index of a cooking utensil (1a, 1b, 11) for a predetermined cooking temperature with, the aim of assessing nutritional gain, said cooking utensil comprising a bottom (2a, 2b, 10) having a cooking surface (3a, 3b, 10a). The method comprises: a) bringing the cooking surface (3a, 3b, 10a) to said predetermined cooking temperature by using heating means (4), the heating of the surface resulting in a deformation of the bottom (2a, 2b, 10) b) determining a minimum quantity of fat (9, 9a, 9b) necessary to cover the entire cooking surface (3a, 3b, 10a) of the bottom (2a, 2b, 10) deformed in this way at said predetermined cooking temperature, by pouring the minimum quantity of fat (9, 9a, 9b) necessary to cover the entire cooking surface (3a, 3b, 10a) or by calculating said minimum quantity of fat (9, 9a, 9b) necessary to cover the entire cooking surface (3a, 3b, 10a) by recreating the cooking utensil (11) deformed in this way by means of a computer equipped with a computer assisted design software program, said minimum quantity of fat (9, 9a, 9b) making it possible to define the performance index of the cooking utensil (1a, 1b, 11) for a predetermined cooking temperature.
