Season the chicken with 1 teaspoon each salt and pepper. Add the olive oil to a dutch oven and cook until browned. Remove the chicken to a plate.
Add the celery, carrots, garlic, onion, rosemary, sage and thyme to the pot and cook, stirring, for 1 minute. Add the wine and stir, scraping up the bottom of the pot. Cook until the wine is reduced by at least half, about 2 minutes. Add the broth, rice and 1⁄2 cup water and stir.
Add the chicken and any juices from the plate; add the bay leaf. Bring to a boil and simmer for 15 minutes.
Meanwhile, in a small bowl, mash together the butter and flour with a fork to make a paste.
Add the butter mixture, stirring to thicken. Add the kale and cook 2 minutes. Stir in the milk and bring to a simmer. Just before serving, remove the bay leaf, add the lemon juice and stir. Season with salt and pepper.