Chop onion and garlic, and put it at the bottom of a HOT rice cooker with some oil to get it to start browning.
While the rice cooker is heating up the onions and garlic, dice your chicken.
Add chicken to the rice cooker and cook until browned.
Add chicken broth, diced tomatoes, brown rice, and drained corn. Drain and rinse black beans; add to cooker. Peel and dice carrots; add to cooker.
Turn rice cooker on to "brown rice" setting, if it has one. Otherwise, turn it on for at least 45 minutes-1 hour. Serve with mango cubes on the side.