Cooking snack foods

A method of cooking expandable snack food precursor pieces, the method comprising the steps of:

• a. providing a bed comprising a plurality of particles, wherein the particles comprise a material which is magnetic or electroconductive or both;
• b. heating the particles in the bed to form a cooking medium in the form of a heated bed of mobile particles, a portion of the particles of the bed having a density higher than uncooked snack food precursor pieces to be cooked in the bed, and another portion of the particles of the bed having a density lower than or equal to expanded cooked snack food pieces, wherein the heating is at least partially by electromagnetic induction, and the mobile particles have a Froude number in the range from 0.01 to 0.5;
• c. providing a plurality of expandable snack food precursor pieces in the cooking medium thereby to cook the expandable snack food precursor pieces to form a plurality of expanded cooked snack food pieces, wherein the heated particles transfer heat into the expandable snack food precursor pieces by thermal conduction;
• and
• d. separating the plurality of expanded cooked snack food pieces from the cooking medium.