A beverage or foodstuff preparation machine (4) comprising: a component processing unit (14) to process a beverage or foodstuff component to prepare a beverage or foodstuff therefrom; and a control system (16) operable to execute a preparation process comprising controlling said component processing unit to prepare the beverage or foodstuff, the control system comprising a user interface (36), wherein the user interface comprises: a contactless sensor (40) operable to sense without physical contact a body part of a user; and a feedback unit operable to provide feedback to a sensor, said body part of a user; and in response to change a value of a parameter associated with the preparation process and to indicate via the feedback unit the change in value.