How to Make It
Heat the olive oil in a large enameled cast-iron casserole. Add the onion, garlic, thyme, 1 teaspoon of salt and 1/2 teaspoon of pepper and cook over moderately high heat, stirring often, until the onion softens, about 5 minutes. Stir in the kale, cover and cook until wilted, about 8 minutes.
Add the chicken stock to the casserole and bring to a boil over high heat. Gradually add the polenta in a thin steady stream, stirring constantly. Lower the heat to moderate and cook, stirring occasionally, until the polenta thickens, 20 to 25 minutes.
Stir in the chicken and simmer until cooked through, 3 to 5 minutes. Season with salt and pepper and serve.