1-First step: Heat the oven and prepare the pan Start by heating your oven to 350°F. Line an 8×8-inch baking pan with parchment paper, leaving a little overhang if possible. That makes it much easier to lift the bars out later.

2-Second step: Brown the butter Place 1 and 1/2 sticks unsalted butter in a skillet over medium heat. Cook it until it turns dark brown and smells nutty, which usually takes about 8 to 10 minutes. Stir in 3/4 teaspoon kosher salt, then let the butter cool slightly.

3-Third step: Mix the shortbread dough In a large bowl, stir together 2 cups all-purpose flour, 1/3 cup granulated sugar, 1/3 cup packed light brown sugar, and 3/4 teaspoon baking powder. Add the browned butter and mix until a dough forms. It will look a little crumbly at first, then come together as you stir. Reserve 3/4 cup of the dough for the topping. Press the rest firmly into the prepared pan. A flat-bottomed measuring cup can help pack it into an even layer.

4-Fourth step: Bake the crust Bake the crust for 15 minutes at 350°F. It should look set but not deeply browned. This short pre-bake creates a firm base that keeps the apple filling from soaking through.

5-Fifth step: Make the apple filling Increase the oven temperature to 375°F. In another bowl, whisk together 2 large eggs, 1/3 cup granulated sugar, 1/3 cup packed light brown sugar, 2 tablespoons all-purpose flour, 2 tablespoons heavy cream, 1 teaspoon apple pie spice, and 1/4 teaspoon kosher salt. Add the sliced apples and toss until every piece is coated. This mixture helps the apples bake into a tender, lightly thickened layer instead of a loose pile of fruit.

6-Sixth step: Layer and top the bars Spread the apple mixture over the warm crust in an even layer. Then crumble the reserved dough over the top. The topping does not need to cover every inch. Gaps are fine and give the bars a pretty rustic look.

7-Seventh step: Bake until golden and thickened Bake the bars for 55 to 60 minutes, or until the top is golden and the filling looks thickened. The center should no longer look wet or loose. If your oven runs hot, start checking near the lower end of the time range.

8-Eighth step: Cool, slice, and serve Let the pan cool for 2 hours before slicing. This waiting time matters because it lets the filling set. After cooling, lift the bars out using the parchment and cut them into 12 to 16 pieces. Serve them as they are, or add a small scoop of vanilla ice cream if you want a dessert-style finish. If you are packing them for a lunchbox or picnic, let them cool fully first so they stay neat.