Braise endive wedges in apple cider vinegar until just softened, then top with crisp prosciutto, toasted walnuts, and Gruyère for a stunning dinner party side dish.
Heat a 12-inch skillet over medium. Add prosciutto. Cook 3 to 4 minutes or until crisp, turning once. Remove; crumble when cool. In same skillet melt butter and heat oil over medium-high. Add garlic; cook and stir 1 minute. Add endive; cook 3 to 5 minutes or until browned, turning occasionally. Add vinegar, salt, and black pepper. Cover tightly with lid.
Reduce heat. Cook 10 to 15 minutes or until the tip of a knife inserts easily into endive. Uncover; sprinkle with cheese. Turn off heat. Let stand, covered, 5 minutes or until cheese melts. Sprinkle prosciutto, walnuts, and rosemary over endive. Serves 8.