Preheat your oven to 350°F (175°C). This step is crucial for getting that perfect bake.
Line a 9x13-inch baking pan with parchment paper, leaving some overhang on the sides for easy removal later.
In a large mixing bowl, combine the melted butter and creamy peanut butter. Whisk them together until smooth. Add the brown sugar, eggs, vanilla extract, and salt, whisking until everything is well combined and creamy.
Gradually add the all-purpose flour to the wet mixture. Use a spatula to fold the flour in gently until just combined. Be careful not to overmix!
Add the dark chocolate chips, milk chocolate chips, and white chocolate chips to the batter. Gently fold them in until evenly distributed.
Spread the batter evenly into the prepared baking pan. Use the spatula to smooth the top.
Place the pan in the preheated oven and bake for 25-30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
Once baked, remove the pan from the oven and let it cool in the pan for about 10 minutes. Then, use the parchment paper to lift the blondies out of the pan and transfer them to a wire rack to cool completely before cutting into squares.
