Chicken casserole/stew in slow cooker/oven:
Season chicken legs/thighs and fry long enough to brown the skin. Then remove.
Saute chopped onion (feel free to add chopped leeks/celery etc if you have them) on medium until translucent. Then add some garlic and teaspoon or so of fennel seeds and fry for another minute or two.
Get a jug of hot chicken stock - use a stock cube or one of those little jelly things, add a tablespoon of tomato paste, a teaspoon of honey, a cinnamon stick and a star anise. Also some white wine if you have it - a small glass is fine (it's even better if you do all this in the pan you've been using, letting the wine bubble for a few seconds first, but it's not essential).
Place onions and chicken into pot you'll cook them in. Pour over the stock/wine, enough to come high up the chicken but don't cover it you want the crispy skins on one side to be just poking out). Add, carrots, cut into squares/rounds.
Pop in slow cooker on low for 8-9 hours or on high for about 4-5. Add a tin of butter beans for the last half hour.
If cooking in the oven, I'd do it at something like 140fan/160 for 90 minutes then another 30-45 minutes with the beans in.
The sauce may be a bit thin. You can either put it on the stove after removing chicken and veg and boil it down. Or just stir in a spoonful of yoghurt. I've also been known to remove the chicken and most of the veggies and just aggressively stir enough that some of the beans land up being a bit mashed and act as a thickening agent.
For DH and DC I strip the chicken and put back into stew. This is particularly good for people who aren't wild about skin as even with the pre-frying, the understide that's been soaking might not stay crispy.