These apple pie bars are made with buttery, shortbread cookie crust, layers of juicy apples, and crunchy, cinnamon streusel.
Note: The apples should be layered on a warm crust, so make sure that by the time the crust is out of the oven, the apple filling and streusel are ready.
Preheat oven to 350°F/180°C. Grease or line a 8x8-inch pan with parchment paper, leaving enough overhang on the sides for lifting the bars out of the pan after baking. Set aside.
To make the shortbread crust: Process flour, sugar, and salt in a food processor until combined. Add butter and vanilla and pulse until mixture becomes crumbly and resembles coarse meal. Alternatively, you can crumble all the ingredients together in a bowl using a pastry cutter. The mixture may seem a bit dry, but it should come together nicely when pinched with your fingers. If you notice it's a bit dry when you do this, add a bit of cold water to bring the dough together. Sprinkle mixture into prepared pan and press firmly into an even layer to form the crust. Bake for 15-25 minutes, until the edges appear golden. While the crust is baking, prepare the apples and streusel.
Make the apple filling: Place the sliced apples, melted butter, and vanilla extract in a medium-sized bowl. Toss to coat. In a seperate bowl, mix together brown sugar, flour, salt, cinnamon, and nutmeg, then add to the apples and toss to combine.
Make the streusel: Combine the flour, oats, brown sugar, cinnamon, and salt together in a medium bowl. Cut in the cubed, chilled butter with a pastry cutter, two forks, or even your hand until the mixture resembles coarse crumbs.
Assemble the apple pie bars: Evenly layer the sliced apples on the warm crust, pressing down gently. The apples should be packed together tightly. Sprinkle the top with streusel and bake for 30-35 minutes until the streusel appears golden brown.
Allow to cool completely on a wire rack at room temperature, then refrigerate for at least 2 hours or until completely set. Then, lift the bars out of the pan using the parchment paper and cut into squares.
Drizzle with caramel sauce, if desired.
Apples: I prefer using tart apples for this recipe to prevent the apple pie bars from becoming too sweet. Granny Smith are ideal, but feel free to use whatever you like or have on hand, just keep in mind sweeter apples will make your bars sweeter.
If you use sweeter apples but don't want your bars to be too sweet, you can reduce the amount of brown sugar you toss with the apples. Feel free to use 3-4 tablespoons instead of 1/4 cup + 1 tablespoon, which the recipes calls for.