Heat the oil in a medium heavy pot (with a lid) over medium-high heat. Sprinkle both sides of the chicken breast with salt and 1/2 tablespoon of the ancho chili powder. Place chicken in the hot oil and brown on each side, 2 - 3 minutes. Remove to a place, leaving behind as much oil as possible.
Add the onion and rice to the pot. Stir for several minutes, until the rice turns from translucent to opaque. Add the garlic and the remaining 3/4 tablespoon ancho chili powder. Cook one minute, and then add the broth and salt to taste. Stir well.
When the mixture comes to a boil, reduce the heat to medium-low. Cover, and cook for 10 minutes.
Cut the chicken breast into 1" pieces. Add them to the pot along with the beans, if using. Recover and cook 12 minutes longer.
Sprinkle the green onions and test a kernel of rice. It should have no more than a hint of chalkiness in the center, in which case you place the cover back on, remove it from the heat and let stand 5 - 10 minutes. If it's not cooked, cook for another 5 minutes or so (at this point I added a tad more chicken broth because I think my pan was too big and the added surface area caused more of the liquid to evaporate; if you use the right size pan this should be fine).
Fluff the mixture with a fork and serve with salsa.