Heat 2tbsn oil in a large frying pan and fry the chicken until cooked through and browned. Remove from the pan and set aside. Fry the leeks and garlic until fragrant and softened (about 5 minutes). Add the cream, mustards and lemon juice and allow to simmer and reduce for 3 minutes. Add lemon juice and place the chicken back into the sauce. Season to taste and serve with the starch of your choice and a sprinkling of chopped parsley.