Abstract: The method in accordance with the invention comprises a rolling of the liquid slag between at least two cooling rolls of metal, preferably steel, the temperature of and the distance between the rolls being controlled such that a cohesive slag slab is obtained having a solidified surface layer and a melted central layer, the slab still being sufficiently plastic to be shapable, a shaping in conjunction with the rolling or after the same, of the slab into briquettes and a recovery of heat at least from the shaped briquettes, preferably after these have been separated from each other, via any suitable cooling means or medium.The apparatus in accordance with the invention comprises at least two cooling rolls (1) arranged to roll out the liquid slag into a cohesive, shapable slab, means (4) for briquetting the slab and means (5,7) for recovering heat from the shaped briquettes.