01 -
Preheat oven to 350°F (177°C). Line a 9 x 13-inch rectangular baking pan with parchment, allowing a slight overhang for easy removal.
02 -
In a large mixing bowl, whisk the melted unsalted butter with packed brown sugar until the mixture is smooth and glossy.
03 -
Add eggs one at a time, beating well after each addition, then blend in the pure vanilla extract until thoroughly combined.
04 -
Fold in all-purpose flour, baking powder, and kosher salt just until the batter is evenly incorporated, taking care not to overmix.
05 -
Gently stir in butterscotch baking chips and toffee bits to distribute evenly throughout the batter.
06 -
Transfer the batter to the prepared pan, smoothing the top. Bake for 25 to 30 minutes, or until the top turns golden and the edges are set.
07 -
Allow bars to cool completely in the pan. Lift out using parchment overhang and cut into uniform squares for serving.