In a medium saucepan, melt the butter over medium heat, stir until melted. Pour over white chocolate chips, let rest for 5 minutes then whisk until smooth. Cool for about 30 minutes.

In a large mixing bowl, combine the cooled mixture with granulated sugar and whisk until blended. Add vanilla extract and eggs, mixing until smooth.

Fold in flour and salt gently, then add blueberries delicately to maintain their shape.

Preheat oven to 350°F. Line an 8x8 inch pan with parchment paper, pour batter in and smooth the top.

Bake for 35 to 45 minutes until edges are golden and a toothpick comes out with a few moist crumbs.

Let cool in the pan for 10 minutes, then lift out to cool completely on a rack before slicing.