Rice dumpling is a rice cake (mochi) covered with coarse sweet red bean paste.
Glutinous rice has finished to steam. It is delicious to eat as it is, too.
Steamed rice is put into the large mortar and is pounded by a large wooden pounder.
When Poirot is pounding, Marple turns the rice and add water in the mortar between hammer strokes.
After pounding, rice cake is torn to pieces and made in round shape.