Preheat oven to 200°C (390°F). Divide the leeks into 4 bunches, wrap a slice of prosciutto around each and place in a baking dish. Add the stock, butter and thyme, cover with aluminium foil and cook for 20 minutes. Heat a large non-stick frying pan over high heat. Brush the chicken with oil and sprinkle with salt and pepper. Cook, skin-side down, for 3–4 minutes, turn and cook for a further 2 minutes. Remove the leeks from the oven, top with the chicken and bake, uncovered, for a further 12−15 minutes or until the chicken is cooked through and the leeks are tender. Serve with the mascarpone mashed potato and green beans with French vinaigrette. Serves 2.