Prepare the vegetable broth: put a saucepan over the heat with the water, the vegetables, washed and cleaned, and a small pinch of salt; leave to simmer slowly for about half an hour. In the meanwhile, cut a slit in the rounded side of the chestnuts. If you have the possibility, roast them over a fire in a perforated pan; if not, in the oven at 200 °C, turning them over from time to time. After roughly 20 minutes (half an hour, in the oven) check to see if they’re cooked: if the skin comes off easily it means that they’re ready. Tip the chestnuts onto a damp cloth, wrap them up and leave them like that for 10 minutes, then peel them and put them to one side. Tie up the pork loin with kitchen string. Crush the cloves of garlic with a garlic press or finely chop them; sprinkle the garlic all over the pork and season with salt and pepper. Insert the sprigs of rosemary between the meat and the string, one on top, one on the bottom. Use a fork to beat the oil and honey together in a bowl and pour the mixture into the bottom of an oven dish. Put the meat in as well and cook it in the oven, at 180 °C, for about half an hour. Check to see when the oil begins to sizzle, take the dish out, pour the white wine over the meat, let it evaporate, then use the liquid that has formed to baste the pork. When it has browned, turn it over so that it cooks on the other side. After half an hour, put the roast chestnuts in the oven dish as well, mix them thoroughly with the oil and juices and put back in the oven for another 20 minutes. Then take the dish out of the oven: the pork should be nicely browned. Leave it on a chopping board to “rest” and pour all the liquid that has formed, along with the chestnuts, into a heavy-bottomed frying pan. Add the broth and the flour (mixed with a tablespoon of broth), and simmer over a moderate heat until the sauce thickens. Remove the string from the meat and slice it. Place the slices on a dish and serve with the sauce, while it’s nice and hot, and the chestnuts as a garnish.