Heat the oven to 220C/200C fan/gas 7. Rub 1 tbsp oil over the chicken and season well, then put skin-side up in an ovenproof casserole dish or roasting tin and bake for 20-25 mins until crisp and golden, but not cooked all the way though. Remove from the dish and put on a plate.
Add the remaining oil to the dish, mixing it with the chicken fat. Tip in the onion and garlic, then bake for 5-8 mins until the onion is tender.
Pour in the wine, stirring it with the onions, then leave to evaporate slightly in the residual heat before adding the bay, thyme, rosemary, parsley stalks and tomatoes. Dissolve the stock cube in 300ml boiling water and pour this in, then add the vinegar, capers, if using, olives and orzo. Stir well and season.
Nestle the chicken back in the pan, skin-side up, and roast for 20 mins until the sauce is thickened, the orzo is tender and the meat is cooked through. Give it a stir, then leave for 10 mins for the orzo to absorb the excess liquid. Scatter over the parsley leaves to serve.