In a medium nonstick pot on the stove, combine sugar, cornstarch, cinnamon, vanilla extract, and salt with 1/2 cup cold water. Mix until the ingredients dissolve. Add apples and stir. Bring to medium-high heat and, stirring frequently, cook until apples have softened, about 7 to 10 minutes.
Reduce heat to low and, stirring often, cook until thick and gooey, 1 to 2 additional minutes. Transfer to a bowl and set aside to cool. This is your pie filling.
Prepare a large baking sheet by lining it with foil and/or spraying it with nonstick spray. Set aside.
Place egg roll wrappers flat on a dry surface. Set out a small dish of water. Dip your finger into the water, and run it along all of the wrapper edges. Repeat as needed while preparing your pockets, as it will help seal them. Starting 1/2 inch from the bottom, place about 1/3 cup pie filling along the bottom half of each wrapper, leaving a 1/2-inch border on the sides.
Fold the top 1/2 of each wrapper over the filling, so that the top edge meets the bottom and the filling is encased with a border on 3 sides. Dab each border with water, and fold each inward about 1/4 inch to lightly seal. Press firmly along the borders with the prongs of a fork to seal completely.
Carefully transfer to the baking sheet. Repeat this process with remaining wrappers and filling, leaving you with 6 pie-lets.
Spray the top of each pocket with 3 sprays butter. Bake in the oven until the edges begin to brown, 15 to 18 minutes.
Allow to cool for 5 minutes. Top with additional cinnamon and whipped topping, if using. Dig in!