I first combined pecans and butterscotch in these blondies because they were my mom-mom's favorite flavors. When she loved them, they became a family favorite and I baked them for her every chance I got. They are fantastic when sliced warm and topped with ice cream. They also make the perfect addition to a friendly care package.
Preheat the oven to 350 degrees F. Spray a 9-inch square baking pan with nonstick cooking spray, line it with parchment paper, then spray the parchment. Set aside.
Place the butter in a medium saucepan and cook over medium-high heat, stirring occasionally, until deep golden, 3 to 5 minutes. Immediately pour into a medium heatproof bowl. Add the brown sugar, salt and baking powder. Whisk to combine. Whisk in the vanilla, whole egg and yolk until smooth.
Add the flour to the wet ingredients and stir with a rubber spatula until nearly combined. Reserve about 2 tablespoons each of the butterscotch chips and pecans, then stir the rest into the batter until evenly combined.
Spread the batter into the prepared pan. Sprinkle the reserved pecans and butterscotch chips evenly over the top then press into the top of the batter.
Bake until golden and a toothpick inserted near the center comes out with a few moist crumbs, 32 to 34 minutes. Let cool in the pan then cut into 16 squares.