1. Heat the olive oil in a non-stick skillet over medium heat. Add the onion and cook until the onion becomes tender, about 4 minutes. Add the garlic and cook 1 minute more.
2. Turn the heat up to medium-high. Season the chicken with salt and pepper and add it to the skillet. Saute the chicken until it is golden brown on all sides, about 4 minutes.
3. Quickly add the chicken broth and stir with a wooden spoon to release any caramelized bits that are stuck to the pan. Cook until the chicken broth has reduced by half. Stir in the mustard.
4. Serve with Skinny Mashed Potatoes or Rice Pilaf .