1 cup (2 sticks) unsalted butter, softened to room temperature
1/3 cup granulated sugar
1/4 cup lightly packed light brown sugar
1 teaspoon pure vanilla extract
2 cups all-purpose flour
3/4 teaspoon kosher salt
1/3 cup chopped walnuts
1/2 teaspoon ground cinnamon
For the Filling
1 1/2 pounds Golden Delicious apples, peeled, quartered, cored, and sliced into 1/4-inch thick slices (I used about 11/2 larger apples)
1 1/2 pounds Braeburn apples, peeled, quartered, cored, and sliced into 1/4-inch thick slices (I used about 11/2 larger apples)
1 tablespoon fresh lemon juice
3 tablespoons granulated sugar
3/4 teaspoon ground cinnamon
1/4 teaspoon freshly grated nutmeg
2 tablespoons unsalted butter
1 teaspoon cornstarch
For the Glaze
3 tablespoons unsalted butter, melted
1 1/2 cups powdered sugar
splash of whole milk
pinch of salt
Place a rack in the center of the oven and preheat oven to 375 degrees F. Line an 8×8-inch square pan with parchment paper so that the paper hangs over two edges of the pan about two inches. This will make the pie bars easier to remove after it’s baked. Lightly spray the pan with non-stick cooking spray and set aside.
For the crust, place the butter, sugars, and vanilla in the bowl of an electric stand mixer fitted with a paddle attachment and beat on medium speed for 3 to 5 minutes, until light and fluffy.
Stop the mixer and scrape down the sides of the bowl. Add the flour and salt and mix on low speed until just combined.
Scatter two-thirds of the dough into clumps in the prepared pan, flour your fingers and press the dough across the bottom of the pan and up the sides of the pan about 1/2-inch.
Refrigerate for 15 minutes.
Bake for 18-20 minutes, until the crust is golden brown and set aside to cool while you prepare the topping and filling.
In a small bowl combine the remaining crust, walnuts and cinnamon. Stir until combined and set aside.
To make the filling, combine both kinds of apples and lemon juice in a medium bowl. Add the sugar, cinnamon, and nutmeg and toss to coat.
Melt the butter in a medium saucepan. Add the seasoned apples and simmer over medium-low heat, stirring often, for 12 minutes until the apples are tender and some of the liquid has evaporated. Add the cornstarch and toss for 1 minute more.
Spread the apples evenly over the crust, leaving a 1/2-inch border.
Pinch medium pieces of remaining dough with your fingers and drop them evenly over the top of the apple mixture (they won’t cover the top completely). Bake for 25 to 30 minutes until the topping is brown.
Allow to cool completely.
To make the glaze, in a small bowl whisk together browned butter, powdered sugar, a plash of milk and pinch of salt. Whisk until smooth. Spoon into a ziplock bag and cut a tiny tip off one corner of the bag. Drizzle glaze over cooled bars before slicing into 9 slices.
Store, wrapped individually or covered in plastic wrap in the refrigerator for up to 5 days.