The installation (1) comprises: a vacuum expansion chamber (4), having an inlet (4a) provided with a first gas- tight valve device (5) for receiving a flow of semi-finished pieces (3) prepared starting from a confectionery compound and including particles, such as air bubbles and/or powders, capable of causing an expansion thereof under vacuum, and an outlet (4b). In chamber (4) there is provided a rotating drum (7) having a grille structure, intended to receive and transfer to the outlet (4b) of said chamber (4) a flow of said semi-finished pieces (3), in a controlled period of time sufficient to allow an expansion thereof under vacuum. A cooling and conveying apparatus (10) under vacuum, at a controlled temperature, has an inlet coupled with the outlet of the expansion chamber (4), and an outlet having an associated second gas-tight valve device (18) for discharging the expanded and cooled confectionery products (3). This apparatus (10) includes at least one cooling and conveying unit (11-14) comprising a conduit under vacuum (11 a- 14a) in which there is provided a worm conveyor device (11d-14d 11e-14e) including a flexible spiral screw (11e-14e) intended to cause a displacement of the expanded pieces (3) at a controlled speed.La instalación (1) comprende: una cámara de expansión de vacío (4), que tiene una entrada (4a) provista de un primer dispositivo de válvula hermético (5) para recibir un flujo de piezas semiacabadas (3) preparadas empezando a partir de un compuesto de confitería y que incluye partículas, tales como burbujas de aire y/o polvos, capaces de provocar una expansión del mismo bajo vacío, y una salida (4b). En la cámara (4) se proporciona un tambor giratorio (7) que tiene una estructura de rejilla, destinada a recibir y transferir a la salida (4b) de la cámara (4) un flujo de las piezas semiacabadas (3), en un período de tiempo controlado suficiente para permitir una expansión del mismo bajo vacío. Un aparato de refrigeración y transporte (10) baj
