Heat a large roasting pan on the stove and add the oil. Once the oil is hot, sear the chicken pieces on all sides until they are golden brown. Place the chicken skin-side up.
Add the garlic, cut side down, to the pan, followed by the leeks. Stir the leeks around in the oil to coat them.
Pour in the white wine and let it simmer for two minutes, then add the stock. Use a wooden spoon to scrape up any browned bits from the bottom of the pan.
Turn off the heat and add the thyme sprigs, butter beans, and spinach, placing them around the chicken. Season with a pinch of salt and pepper, then mix everything together.
Transfer the pan to the preheated oven and bake for 35–40 minutes, or until the chicken is fully cooked. Stir the contents occasionally to ensure even cooking.
Remove the pan from the oven and let it rest for five minutes before serving in warm, shallow bowls.
