Kasha is at least a thousand years old and has historically been eaten in Central and Eastern Europe. In the United States, we commonly eat kasha as a buckwheat groat. However, in Europe, kasha refers to porridge that can be made from wheat, barley, oats, millet, or any other grain.
Kasha is generally attributed to have originated in Russia. Kasha is a common filling to put in a knish, which is a ground meat and mashed potato savory pastry covered in dough.