Heat half the oil in a non stick pan, then brown the chicken all over. Add half the chopped rosemary, stir to coat, then set aside on a plate.
In the same pan, heat teh rest of the oil, then gently cook the onion for about 5 mins until soft. Add the garlic, anchovies & remaining rosemary, then fry for a few mins more until fragrant. Pour in the tomatoes & capers with the wine, if using, or 75ml water if not. Bring to the boil, then return the chicken pieces to the pan. Cover, then cook for 20 mins until the chicken is cooked through. Season & serve.