In a medium saucepan over medium heat, melt 1 cup of unsalted butter. Once melted, add 1 cup of white chocolate chips and remove from heat, letting it rest for about 5 minutes. Whisk until smooth and well-combined. Allow the mixture to cool for 30 minutes.

In a large mixing bowl, combine the cooled butter and white chocolate mixture with 1 cup of granulated sugar, whisk until well incorporated. Mix in 1 teaspoon of vanilla extract and 2 large eggs one at a time until smooth.

Gently fold in 1.5 cups of all-purpose flour and 0.5 teaspoon of salt. Carefully fold in 1 cup of fresh blueberries.

Preheat your oven to 350°F (175°C). Pour the batter into an 8x8-inch parchment-lined baking dish and smooth the top. Bake for 35 to 45 minutes, until the edges are golden and a toothpick inserted into the center comes out with a few crumbs.

Let the blueberry blondies cool completely in the pan on a wire rack. Once set, slice them into 12 to 16 squares.