Preheat and Prepare
Set your oven to 350°F (175°C). Grease a 9×13-inch baking dish and set it aside.
Mix Wet Ingredients
In a large mixing bowl, combine the brown sugar and melted butter. Whisk or beat until the mixture is smooth and glossy. Add the eggs and vanilla extract, and mix well until fully incorporated.
Incorporate the Dry Ingredients
In a separate bowl, sift together the flour, baking powder, and salt. Gradually fold the dry mixture into the wet mixture, mixing until just combined. Be careful not to overmix to maintain that soft, chewy texture.
Fold in Add-ins
Stir in the butterscotch chips and optional chopped nuts until they’re evenly distributed throughout the dough.
Bake to Golden Perfection
Spoon the dense dough into the prepared baking dish, spreading it evenly. Bake for 55 to 60 minutes. If the top starts to brown too quickly, loosely tent the dish with foil for the last 10–15 minutes of baking.
Cool Completely Before Slicing
Let the bars cool entirely in the pan. This step is key for achieving the ideal chewy consistency and clean edges when slicing.
