Preheat oven to 400 degrees. Wash and dry all produce. Slice brussels sprouts in half (or into fourths if they’re large) and cut oﬀ the root. Cut sweet potatoes in medium, even-sized pieces. Cut lemon in half. Chop parsley.
In a small bowl, mix the sage, parsley, juice of the lemon, 1 tablespoon oil and chicken breasts. Let sit for 5-10 minutes to marinate.
Put sweet potatoes in a large pot. Cover with water. Bring to a boil.
Heat a large pan over medium-high heat, add 1 tablespoon oil and chicken breasts. Cook until you see a brown crust around the chicken breasts. Once you see the crust, put in a casserole dish.
Add 1 cup of chicken stock and chopped brussels sprouts to casserole dish. Cover casserole dish with foil. Bake in oven for 20 minutes, or until internal temperature of chicken reaches 165 degrees with a meat thermometer.
Sweet potatoes are done when you can easily poke them with a fork. Drain the water and return them to the pot. Mash sweet potatoes with butter, pepper and cinnamon.