Apple Crisp-Browned Butter Bars

1 . Stage

Cook 3/4 cup butter in a large skillet over medium-low heat until melted and light brown, 12 to 15 minutes. Keep an eye on it; it can burn. Pour into a bowl. Freeze until solid, about 30 minutes.

2 . Stage

Meanwhile, for the filling melt 2 tablespoons butter in the same skillet. Add apples, 2 tablespoons brown sugar, 1 teaspoon cinnamon, lemon juice, nutmeg, and pinch of salt. Cook, stirring occasionally, until apples are golden brown and caramelized, about 15 minutes. Remove from heat. Add 3 tablespoons brown sugar; toss to coat.

3 . Stage

Preheat the oven to 375 degrees F (190 degrees C). Line a 9-inch square baking pan with enough parchment paper to create an overhang on all sides.

4 . Stage

Stir together flour, oats, 2/3 cup brown sugar, baking powder, 1/4 teaspoon cinnamon, and 1/4 teaspoon salt in a bowl. Coarsely shred frozen browned butter or chop into small pieces. Cut butter into flour mixture until mixture resembles coarse meal. Add egg yolk and vanilla; stir with a fork just until a crumbly dough comes together. Press about two-thirds of the dough (2 2/3 cups) in an even layer in the prepared baking pan.

5 . Stage

Bake until lightly browned, about 10 minutes.

6 . Stage

Spread apple mixture over the crust. Crumble remaining dough over top. Bake until golden brown, about 25 minutes. Let cool completely on a wire rack. Using parchment sides to lift bars, transfer to a cutting board and cut into squares.