Preheat the oven to 325F. Spray an 8x8-inch baking dish with nonstick spray then line with parchment paper (the parchment paper should hang slightly over the edge of the pan to help you remove the bars after baking.) The nonstick spray will help the parchment stick to the baking dish.
Get another piece of parchment paper and place the baking dish on top. Using a pencil, trace an outline of the bottom of the pan onto the parchment. Set aside.
In a medium bowl add 1 1/2 cups all purpose flour, 1 cup almond flour, and 1/2 teaspoon kosher salt and stir to combine. Set aside.
In a large mixing bowl add 1 cup (2 sticks) unsalted butter, room temperature and 1 1/2 cups powdered sugar and mix with an electric hand mixer (or stand mixer) until fluffy.
Add 1 large egg and 1 teaspoon vanilla extract and mix well.
This next part is recommended to do by hand. To the bowl add in the dry ingredients (the flour mixture) and mix by hand until combined.
You are going to take half of that prepared dough and put it into the baking dish and spread it out evenly (I just used my clean hands).
Then you are going to take the other half of that prepared dough and place it onto the parchment paper that we outlined earlier. Press the dough down evenly so it fits into that square as best as possible. Set all this aside while you make the filling.
For the brown sugar filling:
In a bowl, add 1 cup light brown sugar, packed, 1 Tablespoon ground cinnamon, 2 Tablespoons all purpose flour, 2 Tablespoons unsalted butter, melted and 1 Tablespoon pure maple syrup and mix well. It will look a bit like wet sand.
Crumble this mixture on top of the shortbread filling layer in the baking dish. Just lightly press it down.
Now you are going to take that other half of the shortbread dough on the parchment paper with the square drawn on it and gently flip it onto the brown sugar filling layer and then carefully peel back the parchment paper. If the dough sticks just take a spatula or butter knife and gently scrape it off the paper.
If necessary, just take your fingers and make sure it’s evenly spread out and not crumbly.
Bake the bars, uncovered, (on the middle rack) for about 40-45 minutes or until the edges are light golden brown in color.
When finished baking, let the bars sit at room temperature to cool for about 30 minutes then transfer to the refrigerator to cool for an additional hour (uncovered). I do like to put a thick dish towel under the baking dish before putting it into the fridge just to protect the glass shelf.
Once the bars are chilled, you can work on the icing.
For the cinnamon icing:
In a bowl, add 3/4 cup powdered sugar, 1 teaspoon ground cinnamon, 2 Tablespoons unsalted butter, melted and cooled, 1 Tablespoon pure maple syrup and 1 Tablespoon milk. Whisk together until combined well. If the icing is too thick add an additional Tablespoon of milk and continue to whisk. You can add a bit more milk at a time until it reaches your desired consistency.
Then spread onto the bars. Optional: sprinkle with a bit of flaky sea salt on top.
You can enjoy the bars right away or allow the icing to set up a bit before slicing into 9 bars. Note: You can slice these into 12 smaller bars as they are pretty rich.
Notes
Please refer to my FAQ’s (Frequently Asked Questions) and ingredient list above for other substitutions or for the answers to the most common questions.