Place cauliflower and stock in a saucepan over high heat and bring to a boil. Cook for 8-10 minutes, or until cauliflower is tender.
Drain cauliflower and place in a food processor. Add the cream, salt and pepper and process for 1-2 minutes, or until smooth (we use a stick blender). Set aside and keep warm.
Heat a large non-stick frying pan over high heat. Brush chicken with oil and sprinkle with salt and pepper. Cook the chicken skin side down for 2-3 minutes, or until browned. Turn and cook for a further 5 minutes, or until cooked through. Remove from the pan and keep warm.
Add the butter to the pan and cook for 2-3 minutes, or until golden brown. Add the sage and vinegar and cook for a further 1 minute, or until the sage is crispy.
Spoon the cauliflower puree onto serving plates, top with the chicken and spoon over the sage butter.