Sauté leeks in 2 tablespoons melted butter in a large skillet or sauté pan over medium heat 5 minutes. Add endive and next 4 ingredients. Simmer 3 minutes; add whipping cream. Simmer, uncovered, over medium-high heat 10 minutes or until cream is reduced by half. Stir in 1 tablespoon butter and 1 tablespoon chopped chives.
Meanwhile, cut puff pastry sheet into thirds along fold lines. Cut each strip into 5 (2"-wide) rectangles; place on an ungreased baking sheet. Bake at 425° for 15 minutes or until puffed and golden; cool 3 minutes.
To serve, gently cut off top of each puff pastry, and spoon about 3 tablespoons endive filling onto puff pastry bottom; replace top. Garnish, if desired. Serve immediately.