A homogenising and kneading mixer comprising a premixer (12) placed upstream from a kneader and at least two kneading screws (20, 21) in turn connected with a vacuum tank (37) feeding final compression screws (44), in which the kneader has a containment cylinder (19a, 19b) and respective kneading screws (20, 21) realised in portions of different diameter, a first portion of smaller diameter (19a, 20a, 21a) arranged at a pasta scrap feeding conduit (25) and a second portion of greater diameter (19b, 20b, 21b) arranged at the premixer (12).