Disclosed is a crisp snack food product that is prepared and cooked to improve or maintain as close to original the shape, colour, flavour and texture of the original food stuff. The food product is prepared in a first phase from thin food pieces of raw fruit, vegetable or gelatinizable proteins, by blanching them (if necessary) and drying them without adding oil. A second phase takes place in a vacuum chamber, where the dried thin food pieces are exposed to heat to expand them, are quickly removed from the heat source and are cooled, before being removed from the vacuum.
