9 tablespoons unsalted butter, softened, plus more for pan
1 2/3 cup all-purpose flour
1 teaspoon baking powder
3/4 teaspoon coarse salt
1 cup packed light brown sugar
2 large eggs
1 teaspoon pure vanilla extract
2/3 cup butterscotch chips
1/4 cup toffee bits
Preheat oven to 350 degrees.
Line a buttered 8 inch square baking pan with foil or parchment paper, allowing a 2 inch overhang.
Butter lining (excluding overhang); set pan aside.
Whisk together flour, baking powder, and salt in a medium bowl; set aside.
Put butter and sugar in the bowl of an electric mixer fitted with a paddle attachment; mix on medium speed until pale and fluffy, about 3 minutes.
Add eggs and vanilla; mix until combined.
Reduce speed to low.
Add flour mixture, and mix, scraping down sides of bowl, until well combined.
Mix in butterscotch and toffee.
Pour batter into prepared pan; spread evenly with a rubber spatula.
Bake until golden brown and a cake tester inserted into blondies (avoid center and edges) comes out with a few crumbs but not wet, 42-45 minutes.
Let cool slightly in pan, about 15 minutes.
Lift out; let cool completely on a wire rack before cutting into squares.
Blondies can be stored in an airtight containier at room temperature up to 3 days.
Makes 9 large squares or 16 small squares.