Hopscotch Dessert Bars

12 tablespoons unsalted butter (6 ounces; 170 g)

Cooking spray

2 1/4 cups all-purpose flour (10 1/8 ounces; 287 g)

3/4 teaspoon Diamond Crystal kosher salt; for table salt, use half as much by volume

3/4 teaspoon baking soda

1/4 teaspoon baking powder

2 tablespoons neutral cooking oil, such as canola

1 1/2 cups packed dark brown sugar (11 1/4 ounces; 320 g) 

1/2 cup granulated sugar (3 1/2 ounces; 99 g)

2 large eggs

2 teaspoons (10 ml) vanilla extract

3/4 cup butterscotch chips (about 4 1/2 ounces; 128 g); see notes

1/3 cup pretzel twists (1 ounces; 28 g), broken or crushed into 1/2 pieces or smaller

Flaky sea salt, such as Maldon

1/3 cup white chocolate chips (2 ounces; 57 g)

Adjust oven rack to middle position and preheat oven to 350°F (175°C). In a medium saucepan, heat butter over medium heat, swirling pan occasionally, until butter smells nutty and milk solids start to turn golden brown, about 6 minutes. Immediately remove saucepan from heat, and continue swirling until milk solids are brown, about 30 more seconds; transfer to a large bowl and set aside.

Line a 13- by 9-inch baking pan with parchment paper, leaving 2 inches of overhang on the long sides. Coat pan lightly with cooking spray. In a medium bowl, whisk together flour, salt, baking soda, and bakind powder; set aside.

Whisk oil, brown sugar, and granulated sugar into browned butter in a large bowl until smooth and glossy, about 1 minute. Whisk in eggs and vanilla until combined.

Add flour mixture to brown sugar mixture; stir until almost combined. Fold in butterscotch chips until chips are evenly incorporated and no dry streaks of flour mixture remain.

Spread batter evenly in prepared baking pan. Sprinkle pretzels evenly over top, lightly pressing into batter.

Bake until edges are puffed and golden brown, center is slightly puffed, and a wooden pick inserted in center comes out mostly clean with a few wet crumbs (center will be slightly underbaked), about 25 minutes. Remove from oven, and sprinkle with flaky salt. Let cool completely in pan, about 90 minutes.

Once bars are cooled, place white chocolate chips in a small microwave-safe bowl and microwave on high, stirring every 20 seconds, until melted and smooth, about 1 minute total. Drizzle melted white chocolate evenly over cooled bars and let stand until chocolate is set, about 30 minutes.

Using parchment paper overhang, lift bars from pan. Cut into 16 bars and serve.