The invention relates to a method of gasifying carbon-containing compounds incorporating mineral elements and/or potential contaminants, and it also relates to a gasification installation having means for containing a bath of molten slag, means for charging said compounds into said bath, means for injecting at least oxidizer into the bath so that the mixture of carbon-containing compounds and oxidizer is super-stoichiometric, whereby a first fraction of the compounds is pyrolyzed, a second fraction is subjected to a combustion reaction suitable for delivering heat energy to the bath of slag, and a third fraction diffuses into the bath, means for recovering the gas given off by the pyrolysis and the combustion of the first and second fractions, and means for lowering the temperature of a portion of the molten slag so as to allow it to solidify, thereby immobilizing at least a portion of the third fraction of the compounds containing mineral elements and/or potential contaminants.