Electric appliance for heating and/or cooking food with steam

An appliance for cooking and/or heating food comprising an enclosure comprising a container, a lid and a steam generating device, wherein the lid has a steam expansion chamber that is supplied with steam by the steam generating device, the steam expansion chamber comprises a containment wall to delimit one portion of the enclosure, wherein the containment wall is mobile with respect to the container and the lid when the enclosure is closed with the lid, and wherein the containment wall is adapted to be moved by one of (a) steam present inside the steam expansion chamber and (b) a pump adapted to inject air into the steam expansion chamber or suck the air present inside the enclosure.