Preheat the oven to 350° and have ready a greased 8"x8" baking dish.
To brown the butter (optional step), add butter to a small saucepan over medium heat and cook 5-7 minutes, stirring often. The butter is ready when it becomes caramel-like color and has a nutty fragrance. Place a fine-mesh sieve over a bowl and strain the butter. Set aside to cool slightly.
In a medium-sized mixing bowl, whisk together the flour, salt, and baking powder. Set aside.
Add ¾ cup of melted, browned butter to a large mixing bowl, along with the brown sugar, granulated sugar, egg, yolk, and vanilla. Whisk to combine. Add the dry ingredients, and stir until just combined. Add pecans and butterscotch chips (if using) and stir until evenly incorporated.
Bake for 25 minutes and allow to cool.
For Maple Buttercream Icing and Topping (OPTIONAL)
Allow the blondies to cool completely before icing.
In the bowl of a stand mixer fitted with a paddle attachment, combine the cream cheese, butter, and powdered sugar. If you do not have a stand mixer, use a large mixing bowl and a handheld mixer. Begin mixing on low speed, until most of the powdered sugar is mixed in, then increase the speed to medium-high. Mix until well-combined.
Add the salt, extract and desired amount of food coloring (if using), and mix once more.
Spread the icing evenly across the blondies, and sprinkle with pecans and toffee, then drizzle with caramel sauce. Cut into squares, serve, and enjoy.
Notes
Note, the amount of butter in the ingredient list does not match the amount of butter called for in the instructions. This is because if you are making brown butter, the butter is likely to reduce while simmering on the stovetop, so starting out with a higher quantity than needed is necessary.