tThe presence of foam is an important characteristic of chocolate beverages. In Mexico, which is part of ancientMesoamerica, the foam in chocolate has been produced since ancient times mainly through two different tech-niques: by pouring the liquid from one vessel to another and by using the molinillo, which is a chocolate beaterwidely used nowadays. Knowledge regarding the different designs and modes of use of the molinillo has traditionallybeen empirical. In this work, the performance of the molinillo during the preparation of a chocolate beverage wascharacterised through high-speed video, and the foam production at three different levels of immersion (clearance),was measured. Furthermore, the hydrodynamics of the system was analysed. The tip speed reached approximately3 m s−1, and a typical forward-backward cycle lasted approximately 300 ms. A small clearance resulted in a high soliddispersion capacity but a limited foam production, whereas a large clearance improved the foam production butexhibited a poor solid suspension. The results quantitatively revealed the scientific basis underlying the empiricalancestral performance of the molinillo in the dispersion of cocoa solids, the promotion of liquid (water)–liquid (cocoafat) mixing, and the production of foam.