Method and plant to make tesserae (11) for glass mosaic, containing ornamental metal foil (14) inside. The method comprises the steps of positioning a first glass strip (30), with a metal foil (14) associated above, on a work plane (20) including first molding means (22), localized heating of the work plane (20) to obtain a softening of the first glass strip (30), casting a quantity of glass onto the metal foil (14), pressing the semi-worked product (29) in its plastic state, and molding the semi-worked product (29) to define the contours of the tesserae (11), by means of cooperation between second molding means (19) and the first molding means (22). One or more of the steps are performed sequentially in at least one work station (40-49).