Preheat your oven to 350°F (175°C). Prepare an 8x8-inch baking pan by greasing it lightly, or line it with parchment paper for easy removal after baking.
In a large mixing bowl, combine the creamy peanut butter, packed brown sugar, and granulated sugar. Use a robust spatula or mixer to blend the mixture until it becomes smooth and evenly incorporated.
Incorporate the large egg and vanilla extract into the peanut butter mixture, stirring until everything is smoothly amalgamated with no streaks remaining.
In a separate bowl, whisk together the baking powder, salt, and all-purpose flour. Gradually add the dry ingredients to the peanut butter mixture, folding gently to combine until just incorporated. Avoid overmixing to keep your blondies tender.
Carefully fold in the chocolate chips and, if desired, the chopped nuts, ensuring they are evenly dispersed throughout the batter without overworking the mixture.
Pour the rich batter into the prepared baking pan, using a spatula to spread it evenly into the corners and smooth out the top.
Bake in the preheated oven for approximately 20-25 minutes, or until the edges are a beautiful golden brown and a toothpick inserted into the center comes out clean or with a few moist crumbs attached.
Once baked, remove the pan from the oven and allow the blondies to cool completely in the pan set on a wire rack. This cooling step is crucial for achieving the perfect texture before cutting into squares.
Notes
For an elegant touch, dust with powdered sugar or serve with vanilla ice cream.