Heat the oil in a large casserole pot. Season flour with chopped parsley and coriander and a little salt and pepper. Coat liver slices in flour and quickly brown in hot fat to seal in flavour. As soon as both sides are browned, remove and set aside. Add chopped carrots, celery, mushrooms, red and green peppers and bacon and mix together well. Add the stout and water to the vegetables. Then pour in the stock, place liver slices back into the casserole dish and seal in flavours with lid. Place in the oven for about 20 minutes on a medium heat at 200C. Remove casserole and using a slotted spoon take out liver and place onto warmed serving dish. Heat sauce to slightly reduce it, then using a tablespoon of flour and butter, quickly blend together, add this to the vegetables to thicken sauce As soon as the liquid has thickened, spoon sauce over the liver, garnish with fresh coriander and serve immediately.