In a bowl, combine the buttermilk, rosemary, lemon zest and pepper. Add the chicken pieces and mix together. Cover and marinate in the fridge for approx. 12 hr. Turn the chicken pieces once or twice during that time.
Remove the chicken, pat dry and season with salt. Heat the clarified butter in a frying pan. Reduce the heat a little, brown the chicken pieces in batches for approx. 5 mins. per batch, remove. Wipe away the cooking fat and add a little clarified butter if necessary. Sauté the shallots for approx. 5 mins. Add the wine and reduce to approx. half the amount. Add the stock, bring to the boil, reduce the heat. Return the chicken pieces to the pan. Add the rosemary, cover and cook on a low heat for approx. 30 mins. Stir in the lemon zest and juice, season.