There are as many versions of chili as there are chili cooks. This one includes a signature flavor of the American Southwest: masa harina. The Mexican corn flour used for making tortillas and tamales, masa harina is made by grinding corn kernels that have been simmered in a slaked lime solution and then dried. It is sold in well-stocked food stores and in Latin markets. Added to the chili near the end of cooking, masa harina thickens the liquid slightly, giving it body, and imparts a subtle corn flavor.