Get all your ingredients and equipment ready. Put a medium saucepan on a medium heat. Turn the oven on to 220?C/425?F/gas 7.

Pick and finely chop the leaves from the rosemary sprigs and sprinkle them into the pack of chicken. Sprinkle 1 teaspoon of mustard powder over each breast, then season and drizzle some olive oil over the chicken and into the frying pan. Massage and rub these flavours all over the meat. Put the chicken breasts in the pan, skin side down. Wash your hands well. Use a fish slice to press down on the chicken to help it cook. It should take around 18 minutes in total.

Quickly trim the leeks and halve lengthways. Wash them under the cold tap, then finely slice them and add to one side of the chicken pan.

Crush 4 unpeeled cloves of garlic into the pan of chicken. Flip the chicken breasts skin side up, then press down on them again. Stir the leeks and add a good swig of white wine.

Check the chicken is cooked through, then pour 75ml of cream into the frying pan. Cover the pan with tin foil.

Turn the heat off. Transfer the chicken breasts to a board and slice into uneven pieces. Stir 1 heaped teaspoon of wholegrain mustard into the sauce, then taste and adjust the seasoning if necessary. Spoon the sauce on to a platter and put the sliced chicken on top. Drizzle over some extra virgin olive oil and take straight to the table.