Preheat the oven to 400 degrees F. Bake the puff-pastry cups according to package directions. In a large bowl, whisk together the pudding mix and skim milk. Put in the refrigerator for 5 minutes. Fold the whipped topping into the pudding mixture. Spoon or pipe 1 teaspoon chocolate pudding mixture into each puff pastry cup. Top each tart with 2 mini chocolate chips.