Cut the chicken into 4 pieces. Heat the olive oil in a large, heavy-based casserole dish and brown the chicken pieces lightly on all sides. Remove and set aside on a plate.
Add the chopped onion to the dish and sauté for about 5 minutes until softened. Stir in the garlic, rosemary, thyme, tarragon (or oregano), and carrot, cooking for 1–2 minutes until fragrant.
Pour in the chicken stock and bring to the boil. Return the chicken pieces to the pan, cover, and cook gently for 30 minutes.
Stir in the broccoli florets and Brussels sprouts (or kale/green beans). Cover again and cook for 10 minutes until the vegetables are tender.
Add the drained cannellini beans and cook for a further 5 minutes to warm through.
Scatter with freshly chopped parsley and serve hot, either on its own or with crusty bread.