We start with the onionwhich we cut into julienne strips and cook little by little in a wide frying pan with olive oil and over a very slow fire, so that it browns without toasting. With patience and stirring from time to time, in about 20 minutes we will have it perfectly caramelized.
As the belly is fat enough, it will suffice with spread it with a little oil with a silicone brush, and then mark it over high heat on the grill, letting it cook for two or three minutes on each side, starting with the skin side. We are not looking for it to be perfectly cooked because later we will finish it with the onion.
To give it a special touch, you can varnish it with smoke oil that I taught you to prepare a few days ago and thus get an extra flavor. Once the belly is marked on both sides, we put it in the pan in which we have made the onion, add the wine and the fish broth and let it cook for five minutes.
Then, we turn off the heat and cover the pan with the lid of a saucepan and let it rest our stew for five minutes. With this brief cooking and rest, the belly will finish cooking inside, leaving it perfectly cooked, juicy and ready to eat. We serve immediately.