Loosen the skin from the chicken. Drain the spinach in a sieve and press out as much water as possible. Mix with the feta and a little black pepper, then stuff between the flesh and skin of the chicken, smoothing the skin back over the stuffing. Season the chicken all over with a little salt and pepper.
Heat the oil in a frying pan with a lid. Add the chicken, skin-side down, and fry until the skin is browned. Turn it over and cook on the other side, then add the pine nuts and fry until lightly toasted. Add 6 tbsp water, then cover for 15-20 mins until the chicken is cooked through.