Peel the onions: wash the pearl onions briefly, bring a pot of water to the boil and blanch the onions for 60 seconds. Remove them from the pot and dip them in cold water so they stop cooking. When they are cold, chop off the two ends and peel the outer layer (or layers, until you find a fresh one). Set aside.
Parboil the potatoes: chop the potatoes into cubes ~1cm thick (leave the skin on if they are fresh, else peel them beforehand). Add salt to the water you boiled the onions in and bring back to the boil. Toss in the chopped potatoes and let them boil for ~7 minutes; you want them parboiled, not cooked through. You can check with the tip of a knife: the potato should still offer some resistance to the blade. Once parboiled, drain and set aside.
Brown the chicken: choose a deep pan with a lid and if necessary chop the legs in two so the pieces will fit well on the bottom. Check the chicken for small feathers; if there are any, remove them by burning on an open flame. Put the 4-5 tablespoons of flour in a food-safe plastic bag, together with half a teaspoon of salt and a grating of nutmeg (or the ground cloves) and pepper. Put the chicken in the bag, seal it and shake well to coat the chicken evenly; remove it from the bag and shake off excess flour. Add some EV olive oil to the pan and a clove of garlic chopped in half, then turn on the heat to high (you can also add a twig of rosemary, provided you remove all the leaves beforehand, else they'll develop a bitter flavour due to the high temperatures). When the oil is hot and the garlic is sizzling add the chicken pieces and brown them on all sides (remove the garlic if it starts to brown). Remove then the chicken from the pan and set aside.
Prepare the cooking base: set the heat to medium under the pan and deglaze the bottom with a little port wine, scraping with a wooden/plastic spoon. Once the bottom is clean toss in the pearl onions, let them heat up for a minute and then add the rest of the port wine and the shot of Cointreau (or the orange peel). Wait until the alcohol has evaporated - you can tell by smelling the vapours, your nose will stop tingling once the alcohol is gone. If you have removed the garlic at the previous stage, you can add another clove of garlic with the skin on at this stage, if you like it.
Cook the chicken: now that the alcohol has evaporated, add back the chicken pieces to the pan, keeping the skin side up. Add a generous pinch of salt to the liquid and on the exposed side of the chicken. Put two sprigs of rosemary on top of the chicken and add enough vegetable stock (or water) to the pan that the chicken pieces are barely halfway covered. Leave the heat on medium until the liquid starts to bubble, then adjust the heat so that it continues to gently bubble. Put the lid on the pan, leaving a little opening so that some of the steam can escape. Let it cook this way for ~40 minutes. Do not stir during this time but gently shake the pan from time to time just to check that nothing is sticking to the bottom. You can check whether the chicken is done by the fact that the meat comes easily off the bones; you can also poke gently the thighs with a knife to check that the meat has dried up inside but is still soft.
Cook the potatoes: While the chicken is cooking, heat on medium some EV olive oil in a pan with a clove of garlic split in halves. When the oil starts bubbling at the edges of the garlic, add the parboiled potatoes to the pan and a generous pinch of salt. Add a sprig of rosemary to the potatoes and wait until they start to sizzle. When that happens, let them cook, tossing them a few times to make sure they are browned evenly. They will be ready once browned and soft but not falling apart (again, check with the tip of a knife); overall ~15 minutes from when they started to sizzle, but the exact time will depend on how strong the heat, the kind of potatoes, the size of the cubes etc. Tasting a cube from time to time is the best way to ensure they are cooked just right. Turn off the heat, grate a little pepper on the potatoes and set aside. If the chicken is not yet ready, you can reheat them in the pan before serving.
Make the jus: Once the chicken is cooked, remove it gently from the pan. Discard the sprigs of rosemary with care (you don't want to drop a million leaves in the pan at this stage). Remove the pearl onions as well (tongs help) and put them in a bowl. The cooking base should still be somewhat liquid. If this is the case, turn up the heat under the pan and let the liquid thicken to your desired consistency (this is why we coated the chicken in flour, to enable this thickening), stirring and scraping the bottom of the pan. It will take 2-3 minutes; you can wrap the chicken in tin foil in the meantime if you are worried it will get cold (it shouldn't). You can stop when it has the consistency of a jus, but if you prefer you can thicken a bit more and get a gravy. Turn off the heat, taste the jus and adjust the salt to taste.
Serve the chicken in a flat dish, on top of a serving of pearl onions and with a serving of potatoes on the side. Drip the jus onto the chicken and decorate with a sprig of rosemary to add a bit of colour to the dish.
Tip: if you have leftover jus, it is excellent for adding flavour to other dishes. Stir fry some veggies and add the jus midway, serve with a fried egg on top and a slice of toasted bread - you got yourself a breakfast.