Step 1

Preheat the oven to 350°F. Line a 9x9-inch baking dish with parchment paper. Set aside.

Step 2

In a large bowl, whisk together the flour, cornstarch, sugar, and salt until combined.

Step 3

Place the butter cubes in the flour mixture. Mix by hand until the dough is light yellow in color and small crumbs form, rubbing any remaining butter bits into the flour mixture.

Step 4

Press the shortbread mixture firmly and evenly into the lined pan. Using a fork, pierce dough at 1-inch intervals.

Step 5

Bake for 15 minutes. While the shortbread is baking, prepare the apple mixture and the crumble topping.

Step 6

Place sliced apples in a bowl. Add brown sugar, flour, and cinnamon. Stir gently, making sure every piece of apple is coated in the sugar mixture.

Step 7

In a small bowl, whisk together the flour, brown sugar, and cinnamon until combined.

Step 8

Add the cubed butter to the flour mixture. Using your hands or a fork, mix the butter into the flour mixture until the butter pieces are pea-sized or smaller.

Step 9

Once the shortbread crust has baked for the 15 minutes, remove from the oven. Top the crust with the apple mixture.

Step 10

Sprinkle the crumble topping over the apple mixture.

Step 11

Bake for 35-40 minutes, or until golden brown.

Step 12

Allow the bars to cool to room temperature, then transfer to the fridge to chill for at least two hours before serving.

Step 13

Serve drizzled with caramel. (optional)