Preheat the oven to 325°F and butter or line a 9x13 baking dish with parchment paper.

In a stand mixer bowl fitted with a paddle attachment or large bowl using an electric mixer, combine the butter and sugars and mix at medium speed until light and creamy. Then add the vanilla and beat until combined.

Slowly add the flour to the butter mixture on low speed and mix until a smooth, soft dough forms.

Press 1/3 of the dough into the prepared baking pan. Make sure the dough is equal thickness using a tart tamper or measuring cup to smooth it out. Place the remaining ? of the dough in the refrigerator

Bake the base in the preheated oven for 15-20 minutes or until the edges are a light golden brown.

Peel, core, and slice apples to about 1/8th inch thick. Scatter the apples in a saucepan.

Mix the apples with the sugar, cinnamon, ginger, and lemon juice, then add the flour. Cook in the pan or pot over medium heat, stirring frequently until the apples release their juices and are cooked through.

Combine the water and cornstarch in a small bowl with a whisk to create a slurry. Stir this into the hot apple mixture and continue cooking for an additional minute.

Cool on a plastic-lined sheet pan or spread on the par-baked crust. The filling doesn’t need to be cool to assemble and finish baking, but you can make it ahead of time and refrigerate or freeze it until ready to assemble.

Pour the apple filling over the crust and crumble the remaining dough (two-thirds of the dough) over top.

Return the bar to the pre-heated oven to continue baking. Bake until the filling is bubbly and the topping is firm and lightly golden, about 25-30 minutes.

Let it cool before cutting into squares. Serve as they are or like you would apple pie, with salted caramel sauce and vanilla ice cream, of course ?.