Peel apples, slice apples into ⅓” wedges on a cutting board with a non-slip mat with a paring knife, and put into a 9” x 13” baking pan.
Cut butter into ½” cubes and sprinkle over apples.
Smush together cornstarch, sugar and light brown sugar and sprinkle over apples. Cover with tin foil and roast at 400 degrees until tender, about 30 minutes. Uncover and stir.
Strain off liquid from apples. Bring liquid to a boil while stirring continuously until thick about 2 minutes after boiling. Pour back over the apples, add raisins.
Using a rolling pin, roll cobbler topping with a little flour on parchment paper until ¼” thick, tear into pieces and put in a patch work pattern (not overlapping) on top of a baking dish, sprinkle top of dough with a generous amount of cinnamon sugar before baking, bake at 300 degrees until light golden.