In a medium saucepan over medium heat, melt unsalted butter until bubbly and slightly golden, about 3-5 minutes. Remove from heat and pour in white chocolate chips. Let sit for 5 minutes, then whisk together until glossy and smooth. Allow to cool for about 30 minutes.

In a large mixing bowl, add the cooled butter-chocolate mixture and whisk in granulated sugar until fully combined. Stir in vanilla extract and eggs, mixing until thick and creamy.

Gently fold in all-purpose flour and salt to the wet mixture with a spatula, mixing only until just combined. When the flour is almost incorporated, fold in fresh blueberries.

Preheat your oven to 350°F (175°C) and grease or line an 8x8 inch baking dish with parchment paper. Pour the blondie batter into the prepared dish, spreading it out evenly. Bake for 35 to 45 minutes, or until the edges are golden brown and a toothpick inserted comes out clean or with a few moist crumbs.

Let the Blueberry Blondies cool in the baking dish for about 10 minutes. Transfer to a wire rack to cool completely. Cut into squares and serve.