In a large enameled cast-iron casserole or Dutch oven
, heat the oil
until shimmering. Add the onion, bell peppers and garlic and cook over moderate heat, stirring occasionally, until just beginning to brown, about 8 minutes. Add the paprika, caraway and flour
and cook, stirring, for 2 minutes. Add the stock, bay leaves and thyme sprigs, season with salt and pepper and bring to a boil. Simmer over moderately low heat, stirring occasionally, until the peppers are very tender and the sauce is thickened, about 1 hour.