Preheat the oven to 350 degrees
Line a 8" x 10" baking dish with parchment paper.
The crust and crumb layer are one in the same. Begin by combining 2 sticks of salted butter (but into small cubes), 1.5 cups sifted powdered sugar, 1 & 2/3 cups gluten free flour, and 1 teaspoon ground cinnamon. Next roll up your sleeves, get ready to use some elbow
grease, and work all of those ingredients together into crumbs.
I like to use my hands because I can feel when the butter and dry ingredients are incorporated. You may also use a pastry blender or 2 forks. It will take a few minutes to bring this mixture to the right crumb. You do not want sandy crumbs. Keep working. Your crumbs should easily hold together.
Reserve 2 cups (unpacked) of the crumbs in a separate bowl. These will be used later to make the crumb layer. Press the remaining crumbs into the bottom of the prepared baking sheet. Pierce several times with a fork. Bake for 15 minutes at 350 degrees.
For the cheesecake layer, place the cream cheese in the bowl of a stand mixer fitted with a paddle attachment. Cream until light and fluffy. Add in the condensed sweetened milk. Mix until smooth. Add in the egg and cinnamon, mixing until smooth. Pour the mixture over the prebaked crust. Return to the oven and bake for 10 minutes.
While the cheesecake is cooking, work on the apple layer. Melt 2 tablespoon of butter in a large skillet. Stir in the brown sugar. Add in 4 cups of diced apples. Cook over medium heat for 5-6 minutes, stirring very often to prevent sticking and burning. Adjust stove temperature as needed. Stir in one tablespoon of flour and 1 teaspoon of cinnamon. Spread the apples over the cheesecake layer.
Sprinkle the reserved 2 cups of crumbs over the apples.
Bake for 25-30 minutes or until the crumbs are golden.
Allow to cool at room temperature for 2 hours.
Chill in the fridge overnight or for 5 hours.
Cut into bars.
Just prior to serving make the whipped cream. Place 1 cup of heavy whipping cream and 1-2 tablespoons of sifted powdered sugar into the bowl of a stand mixer fitted with a whisk attachment. Whisk on high until the cream thickens.
Spoon or pipe the cream over each bar.