Melt ½ cup of unsalted butter over medium heat until bubbly and lightly golden. Pour melted butter over 1 cup of white chocolate chips in a mixing bowl. Allow to sit for 5 minutes, then whisk until fully combined. Let cool for 30 minutes.

In a large bowl, whisk together the cooled butter-chocolate mixture with 1 cup of granulated sugar until blended and glossy. Stir in 1 teaspoon vanilla extract and add 2 eggs, whisking until smooth.

Gently fold in 1 ½ cups of all-purpose flour and ½ teaspoon of salt with a spatula. Once incorporated, add 1 ½ cups fresh blueberries, folding them in carefully.

Preheat oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment paper. Pour batter into the pan and bake for 35 to 45 minutes until edges are golden and a toothpick comes out clean.

Once baked, let cool in the pan for 20 minutes. For best results, cool completely before lifting out and cutting into squares.