Immediately after unrolling phyllo sheets, spray with nonstick spray. Divide sheets into two stacks of three. Cut each stack into six sections by cutting each in half lengthwise and then into thirds horizontally. You should now have twelve mini stacks.
Prepare a 12 cup muffin pan by spraying with nonstick spray. Gently place each mini stack into a cup, pressing down lightly with your fingers so the dough creates a cup shape. Bake in the oven for 8 to 10 minutes, until lightly browned. Set aside to cool.
In a small unheated pot, combine butter, brown sugar, cornstarch, and cinnamon with 1 tablespoon water. Stir until ingredients have mostly dissolved.
Over medium heat, cook and stir brown sugar mixture until it thickens to a caramel sauce-like consistency.
Reduce heat to low and add the apples. Cook for 3 to 4 minutes, until apples have softened, stirring continuously so the filling does not burn.
Evenly distribute filling among the twelve pastry shells. If you like, top with Reddi-wip just before serving. Enjoy hot or cold!