Preheat your oven to 350°F (175°C). Line an 8x8 inch baking pan with parchment paper, leaving some overhang on the sides for easy removal later.

In a mixing bowl, whisk together the melted butter, brown sugar, and granulated sugar until well combined. The mixture should be smooth and glossy.

Add the eggs one at a time, whisking well after each addition. This helps to incorporate air, giving the blondies a light texture.

Stir in the vanilla extract.

In a separate bowl, combine the sifted flour, baking powder, baking soda, and salt. Gradually add the dry ingredients to the wet mixture, stirring until just combined. Be careful not to overmix, as this can make the blondies tough.

Gently fold in the blueberries and white chocolate chips using a spatula, ensuring they are evenly distributed throughout the batter.

Pour the batter into the prepared baking pan, spreading it evenly with the spatula.

Bake in the preheated oven for 25-30 minutes, or until the edges are golden brown and a toothpick inserted in the center comes out with a few moist crumbs.

Remove the blondies from the oven and allow them to cool in the pan for about 10 minutes. Then, lift them out using the parchment paper and transfer to a wire rack to cool completely.

Once cooled, cut into squares and enjoy!