The present invention provides an assembly for introducing a dose of a mixing substance into a container, said assembly comprising a dosing part (3) and a supply part (2), which dosing part is arranged for receiving the dose and which supply part comprises an outlet (14) for introducing the dose into the container. The dosing part and the supply part are configured to cooperate with one another, such that a pressure chamber having a changeable volume is formed adjacent to the outlet when the supply part and the dosing part are joined together, which pressure chamber functions to enable a pumping action for pumping the dose into and out of the container. The invention further provides a method for inserting such a dose into a container.
