馅 (xian4 or xian4r) is the general term for the filling or stuffing in all kinds of dumplings (such as the 水饺 [shui3 jiao3, boiled dumplings] pictured above). The word is typically erhua‘d, meaning that it is pronounced like “xiar”.
An interesting thing about 馅 is that the meaning has drifted to encapsulated ground meat as sold in the supermarket. I am fortunate to live near a supermarket where the butcher section has ready-to-buy ground beef and ground mutton, which I find myself buying fairly regularly to make chili, meatballs, and tacos.
The word for “grind” is 磨 (mo2) and that works for grinding grains, spices, and coffee, as well as meat. If you need something to be ground on-demand, you’d ask for it to be 磨成粉 (mo2 cheng2 fen3) or 磨成馅儿 (mo2 cheng2 xian4r) if the end result is a powder or meat filling respectively.