Preparation Melt butter with oil in heavy large skillet over medium-high heat. Add onion and sugar. Sauté until onion is lightly browned, about 7 minutes. Add vinegar; stir to blend. Add radicchio, raisins, salt, and pepper. Cook until radicchio is just wilted, about 5 minutes. Transfer to serving dish; sprinkle with pine nuts.
Preparation Melt butter with oil in heavy large skillet over medium-high heat. Add onion and sugar. Sauté until onion is lightly browned, about 7 minutes. Add vinegar; stir to blend. Add radicchio, raisins, salt, and pepper. Cook until radicchio is just wilted, about 5 minutes. Transfer to serving dish; sprinkle with pine nuts.