I really waited for this question, cause i thought, that the plate, and their little Hitbox could be hard to get.
To finish the Minigame, you need to drag the White Plate under the other Dishes to the left, with them on top.
You can only Drag the Plate, not the Dishes on top, thats why you need to click right on the plate.
Little Tip: Grab it a little more right, and try to give the plate a 30 Degree clockwise rotation. Then just move the plate fast, but not too fast, to the left. This should keep the Cup on top, without doping it. (Hope this helps a bit)