One pot, almost no attention, and it improves overnight. The thighs give up enough fat to carry the whole dish.
Skin side especially. An hour is enough for thighs — they are fattier and more forgiving than breast, and you are seasoning rather than transforming.
Wide oven-proof pan, oil, medium heat. Thighs skin down, and do not crowd the pan — two batches if you need to. Eight to ten minutes until the skin is genuinely brown, not beige. Turn for one minute, then take them out.
There will be a lot of rendered fat in the pan. Pour off all but about two tablespoons of it and keep the rest for potatoes.
Onion and carrot into the same pan, medium-low, eight minutes until soft and starting to colour at the edges. Garlic for the last minute, no longer.
Wine in, scrape everything off the base of the pan with a wooden spoon, and let it reduce by half. That brown material on the base is most of the flavour of the finished dish and it will not come off later.
Beans and stock in, rosemary tucked among them. Bring to a simmer, then sit the thighs back on top, skin up — and this matters — with the skin sitting clear of the liquid.
If the liquid covers the skin, it will not crisp and you will have spent ten minutes browning it for nothing.
170 °C, forty-five minutes, no lid. The thighs finish, the beans take up the stock and the skin re-crisps in the dry oven air.
Ten minutes before serving. It is good now and it is better tomorrow — the beans keep absorbing and the whole thing settles into itself. Reheat gently, uncovered, at 160 °C.
Tinned beans are already fully cooked and forty-five minutes at 170 °C is more than they need. Either add them for the last twenty minutes only, or use beans you cooked yourself from dried, which hold their shape far better.
Some breakdown is wanted, though — a handful crushed against the side of the pan thickens the liquid and is the difference between a braise and a soup.