Preheat your oven to 350°F (175°C).
Line a 9x13 inch baking pan with parchment paper, leaving some overhang on the sides.
In a large mixing bowl, combine the melted unsalted butter and creamy peanut butter. Stir until fully blended. Add light brown sugar, eggs, and vanilla extract, mixing well until smooth.
In another bowl, whisk together the all-purpose flour and salt. Gradually add this dry mixture to your wet ingredients, stirring gently until just combined.
Fold in the dark chocolate chips, milk chocolate chips, and white chocolate chips until evenly distributed.
Pour the blondie batter into the prepared baking pan and spread it out evenly. Bake for 25-30 minutes, until the edges are set and the center is just slightly underbaked.
Let the blondies cool in the pan for about 10 minutes. Use the parchment paper overhang to lift them out and place them on a wire rack to cool completely. Slice into squares and enjoy!