A method for liquefying a stream of hydrocarbons from a feed stream, including introducing the feed stream and a first cooling stream into a first heat exchanger, extracting a plurality of partial cooling streams obtained from the first cooling stream from the heat exchanger via separate outlets, introducing each partial cooling stream into an expansion element to produce a plurality of biphasic cooling streams at different pressures, introducing each biphasic cooling stream into a phase separator element to produce a gaseous cooling stream which is diverted from the first exchanger and a liquid cooling stream which is introduced into the first exchanger via respective inlets, evaporating each liquid cooling stream by heat exchange with at least the feed stream and the first cooling stream so as to extract a cooled hydrocarbon stream at the outlet from the first heat exchanger and to extract a plurality of evaporated cooling streams.