Apple Pie Bars

This recipe is adapted from Bon Appetit; the bars are actually better the next day after making them (although delicious warm out of the oven as well).  A bit of work but worth it...

For the crust:
3 sticks unsalted butter, softened
3/4 cup sugar
3 cups flour
1/2 t kosher salt

Preheat the oven to 375º and line a 12 X 17 rimmed baking sheet (a half-sheet pan) with parchment paper. Beat the butter and sugar until light and fluffy (about 2 minutes) and add in the flour and salt at low speed just until a soft dough forms. Press into the prepared pan- this part is fussy and it will seem as though there is not enough dough. Bake for 20 minutes until the crust is light golden.

For the filling:
12-14 tart, firm apples- about 6 lbs (I used Zestar and Honeycrisp but the instructions say to use Granny Smith), peeled and thinly sliced
6 T butter
1/2 cup brown sugar
1 T cinnamon
a good squeeze of lemon

In two large skillets (or you can do this in two batches), melt 3 T of the butter and 1/4 cup brown sugar until bubbling. Add half the apples and cook over high heat until the water is evaporated and the apples are soft and starting to caramelize (but don't overcook or the apples will be dry). This takes about 10-15 minutes. Add 1/2 T cinnamon and a squeeze of lemon to each batch. Let the apples cool.

For the topping:
1/2 cup walnuts (toasted if you're feeling industrious)
1 1/2 cup oats
3/4 cup flour
3/4 cup brown sugar
1/2 t cinnamon
1/4 t baking soda
1/4 t salt
1 1/2 sticks (6 oz.) unsalted butter, cut into cubes

In a food processor, pulse all the dry ingredients. Add the butter and walnuts and pulse until crumbly (like wet sand).

For the bars:
Spread the apple filling over the crust and scatter the crumb topping over the apples. Bake at 375º for about 25-30 minutes until topping is golden.