Sprinkle the chicken breasts with salt and pepper and coat with flour. Heat the olive oil in a heavy frypan and cook the chicken 4 minutes on each side. Set aside.
To the frypan add the shallots and fry 1 minute. Add the chicken stock and bring to the boil. Add the lemon juice and capers. Boil until reduced to 1/2 cup, about 5 minutes. Swirl in the butter and serve over the chicken.