Preheat the oven to 350 degrees Fahrenheit and line a 8” x 8” pan with a piece of parchment paper.

Add all of the ingredients for the shortbread crust and topping to a large bowl and mix until combined. There's no need to separate the wet ingredients from the dry ingredients, as everything can be mixed at the same time. The dough should be slightly crumbly but still press together easily. Measure out ½ cup of the crust mixture and set it aside to use as the crumble topping.

Pour the remaining crust mixture into the prepared pan. Use your hands to press the crust mixture into the pan, creating an even layer. Poke the crust many times with a fork - this will prevent it from bowing up and ensure it is baked evenly.

Bake the crust on the center rack of the oven for 18 to 22 minutes, until it is slightly golden brown around the edges.

While the crust is baking, prepare the apple filling. Peel, core, and slice the apples into thin slices. You will need 6 cups of sliced apples, which should be about 4 to 5 large apples.

Transfer the apple slices to a saucepan along with the water, pure maple syrup, ground cinnamon, and sea salt. Cover the pot and heat over medium-high heat. Bring the mixture to a full boil and cook for 5 minutes. Stir in the flour and the butter until all lumps of flour are dissolved. Note: if there isn’t very much liquid surrounding the apples and the liquid seems relatively thick, you can skip the flour. If, however, there are a lot of watery juices, be sure to add the flour.

Continue cooking the homemade apple pie filling at a gentle boil (reduce the heat to medium if need be), stirring occasionally, until they have softened and reached your desired texture. I like my apples soft, so this takes me about 15 to 20 minutes total. For al dente apples, the whole cooking process will take about 6 to 8 minutes.

Pour the apple filling over the pre-baked pie crust and spread it evenly over the crust.

Sprinkle the reserved ½ cup of crust mixture over the apple layer to use as the crumble topping.

Place the apple pie bars in the oven and bake for 22 to 30 minutes or until the topping begins looking slightly golden brown.

Remove the apple pie bars from the oven and allow them to cool to room temperature before slicing.

I find it’s easiest to pull the full batch of pie bars out of the baking dish and place them on a cutting board to slice them.

Combine 1 cup of powdered sugar with 2 tablespoons of water or fresh lemon juice in a small bowl or measuring cup. Stir well until the lumps of powdered sugar have dissolved and the glaze is nice and runny.

Use a spoon to drizzle the glaze over the apple pie bars.

Serve apple pie bars with a scoop of vanilla ice cream, and enjoy!