The technology includes a device for mixing a liquid and a powdered substance in a vessel. The device includes a body having a planar surface with a grid that includes a plurality of openings and at least two elongated apertures arranged in a circumferential direction. The openings and the elongated apertures are co-planar, with the at least two elongated apertures having a cross-sectional area that is more than twice as large as a cross-sectional area of the openings of the grid. The mixing device further includes a plurality of connection portions that extend between the grid and the rim to mechanically connect the grid and the rim. The connection portions are arranged so that at least two apertures are defined between the rim and the periphery of the grid.
