1. Brush the chicken breasts with half the flavoured butter and marinate for 4 hours in a cool place.
  2. Peel and wash the carrots and shorten the tops to leave about 1 centimetre. Arrange the carrots next to each other in a saucepan.
  3. Add 20g of butter, 1 pinch of salt and sugar and wet with water to just cover them. Cover and bring to a boil, then simmer over low heat for 25 minutes. Remove the cover and allow the water to evaporate. Stir in the butter in a circular motion to coat the carrots.
  4. While the carrots are cooking, peel and wash the potatoes, cut them into slices and brown them in butter. Clean the leek, cook it in water until it is still a little crunchy, and then caramelise it in butter.
  5. Bake the chicken breasts at a low temperature in the oven at 90°C for 50 minutes.
  6. Arrange the supremes and vegetables on a plate and serve with the remaining zaatar butter.