In a saucepan over medium-high heat, bring the water to a boil. Stir in the rice, reduce the heat, cover, and simmer gently for 40 to 45 minutes, or until the kernels puff open. Fluff the rice with a fork and simmer for 5 minutes. Drain any excess liquid from the pan and set aside.
In a large skillet over medium-high heat, heat the oil. Season the chicken with salt, pepper, garlic, and rosemary. Cook for 6 to 8 minutes, turning the chicken once, or until the chicken is no longer pink and the juices run clear.
Add the agave or honey, mustard, and reserved rice to the skillet and cook, stirring occasionally, for 2 to 3 minutes to coat the chicken and rice thoroughly.