In a large skillet, heat butter over medium heat. Add apples; cook and stir 5 minutes. Mix brown sugar, cornstarch and cinnamon; add to apples. Cook and stir 7-8 minutes longer or until apples begin to soften and caramelize. Remove from heat; stir in lemon juice and vanilla. Cool completely., Preheat oven to 400°. On a lightly floured surface, unroll pastry sheets. Roll to 1/8-in. thickness; cut four 5-in. circles from each sheet. Place about 3 tablespoons filling on one half of each circle. Moisten pastry edges with water. Fold pastry over filling. Press edges with a fork to seal or, if desired, pinch edges to seal and flute., Transfer to greased baking sheets. Prick tops of pastry with a fork. Bake until golden brown, 20-25 minutes. Remove from pans to wire racks. , For topping, mix sugar and cinnamon. Brush pies with melted butter; sprinkle with cinnamon-sugar. Serve warm or at room temperature. If desired, top with ice cream.