Using a sharp knife, cut pastry sheet in half. Return half to the freezer. Thaw remaining pastry. On a lightly floured surface, roll pastry into a 14x7-in. rectangle. Cut into two 7-in. squares.
Place an apple on each square. In a small bowl, combine the brown sugar, walnuts and cinnamon. Spoon into center of each apple; top each with 1 teaspoon butter. Gently bring up corners of pastry to center; pinch edges to seal. Place in a shallow 3-cup baking dish coated with cooking spray. Melt remaining butter; brush over pastry.
Bake at 375° for 40-45 minutes or until apples are tender and pastry is golden brown. In a small bowl, combine glaze ingredients. Drizzle over dumplings. Serve warm.