Cut the chicken beast into 4 equal pieces. Dust the chicken with flour then place in a hot frypan and cook until browned on the outside. Remove and place in a ceramic casserole dish.
Slice the leek into 1/2cm rounds, then add to the frypan with the butter. Cook until well softened and starting to brown. Add the wine to the pan and stir to remove any brown bits stuck to the bottom of the pan. Add to the chicken.
Place the casserole dish with the chicken in it in an oven preheated to 180 degrees C and leave until the chicken is cooked through; about 10 minutes. Serve hot with vegetables.