Heat the oil in a medium saucepan over medium-high heat until hot but not smoking. Add the chorizo, and cook for 5 to 6 minutes, until cooked through, browned, and it has rendered its fat. Remove with a slotted spoon and set aside.
Add the onion and chile and cook for a few minutes, stirring a couple times, until they soften. Add the cooking broth from the black beans and rice, stir, and add in the epazote or cilantro and salt, and stir again.
Bring to a rolling boil, cover the pan, and reduce the heat to the lowest setting. Cook for about 15 minutes, or until most of the liquid has been absorbed but there is still some moisture in the pan. The rice should be cooked and tender; if it is not but all the liquid has been absorbed, add a couple tablespoons of water, cover again, and cook for 2 more minutes. Remove from the heat and let the rice rest, covered, for at least 5 minutes.
Fluff the rice with a fork, add the chorizo and mix. Top with more fresh cilantro or epazote and serve.