Start by melting ½ cup of unsalted butter in a medium saucepan over low heat, stirring gently until it's fully melted.

Remove from heat and add 1 cup of white chocolate chips, letting them sit for 5 minutes to soften. Whisk until smooth, then allow to cool for about 30 minutes.

In a large mixing bowl, combine the cooled butter-chocolate mixture with 1 cup of granulated sugar, whisking until fully incorporated.

Stir in 1 teaspoon of vanilla extract and add 2 large eggs, whisking until the batter is creamy.

Gently fold in 1 cup of all-purpose flour and a pinch of salt, then add ½ cup of fresh blueberries.

Pour the batter into a greased and lined 8x8-inch baking pan, spreading it evenly. Bake at 350°F (175°C) for 35 to 45 minutes.

Remove from the oven and cool in the pan for 10 minutes. Transfer to a wire rack to cool completely.

Slice into 12 or 16 bars for serving.