In the skillet, melt 1/2 tablespoon of the butter in 1/2 tablespoon of the olive oil. Add half of the endive and a pinch each of salt and pepper. Cook over moderately high heat, tossing, until browned in spots and just starting to wilt, about 2 minutes. Transfer to the large bowl. Repeat with the remaining butter, olive oil and endive. Let cool.