Season the chicken breasts to taste with salt and pepper. Heat the oil in a large nonstick frying pan, add the chicken breasts and cook over a medium heat, turning once, for 4–5 minutes or until golden all over.
Pour in the orange juice, add the orange slices, and bring to a gentle simmer. Cover tightly, reduce the heat to low and cook gently for 8–10 minutes or until the chicken is cooked through. Add the chopped mint and butter and stir to mix well. Cook over a high heat, stirring, for 2 minutes. Serve immediately.