Wash and dry the endive leaves, including the coarse outside ones. Chop them into 1-inch (2.5 cm) strips. Heat the butter and oil in a saucepan and sauté the onion until soft. Add the endive and stir until it is well coated in the butter and oil. Add the stock and simmer covered for about 10 minutes, or until the endive is wilted. Season with salt and pepper.
At the same time cook the p