Dip container of frozen mix into hot water just to loosen. In 2-quart saucepan, heat frozen mix and water to boiling. Reduce heat; cover and simmer, stirring frequently, until mix is thawed, about 20 minutes. Heat oven to 375'. Place half the potato rounds in ungreased 1 1/5-quart casserole; pour meat mixture over potato rounds and top with remaining potato rounds. Cover and bake 25 minutes. Uncover and bake until potato rounds are brown, about 10 minutes longer.