Preheat the oven to 300°F and line an 8" x 8" square pan with parchment paper. Set aside.

To make the shortbread crust, stir together the melted butter, sugar, vanilla, and salt. Add the flour and stir until well combined. Press the shortbread dough into the bottom of the square pan. Bake for 15 minutes.

While the shortbread is baking, making the apple pie filling by combining the apples, flour, sugar, cinnamon, and nutmeg in a large bowl. Make sure the apples are evenly coated in the mixture.

To make the streusel, mix together the oats, brown sugar, cinnamon, and flour in a small bowl. Cut in the cold butter, a little at a time, mixing well. The mixture should look like big crumbs.

Once the crust has baked, turn the oven up to 350°F. Pour the apple pie filling over the crust and spread evenly. Then, sprinkle the cinnamon streusel on top. Return the pan to the oven and bake for 30-35 more minutes. The streusel will look golden brown.

Wait about 20 minutes before cutting these bars. Once cut, melt the Cookie Butter for about 30 seconds in the microwave. Transfer the melted Cookie Butter to a small plastic baggy and snip one corner off. Drizzle the Cookie Butter over each bar. Enjoy!