A process for manufacturing plasterboard and a plasterboard manufacturing unit are provided, the process including feeding hydratable calcium sulphate and water into a first mixer (2) and into a second mixer (3); feeding in a facing (5); preparing a first gypsum slurry in the first mixer (2); preparing a second gypsum slurry in the second mixer (3); applying the first slurry onto the facing and forming a crude surface layer; applying the second slurry onto the crude surface layer and forming a crude core layer with a density lower than that of the crude surface layer; forming a plasterboard; hydrating and drying the board. This process allows the formation of the different layers of gypsum to be controlled independently.