Heat the oil in a 10-inch skillet over medium-high heat. Add the chicken and cook for 10 minutes or until well browned on both sides.
Add the onion and garlic to the skillet and cook until the onion is tender. Add 1/2 cup broth and heat to a boil. Reduce the heat to low. Cover and cook for 5 minutes or until the chicken is cooked through.
Remove the chicken from the skillet, cover and keep warm. Stir the remaining broth, orange juice and mustard in the skillet and heat to a boil. Cook for 10 minutes or until the sauce is reduced to 3/4 cup. Serve the sauce with the chicken.