Preheat the oven to 325°F
Add butter and 1/2 c of the white chocolate chips to a microwave safe bowl. Heat in the microwave in 15-20 seconds increments until melted. Cool.
In a separate bowl add eggs, sugar and vanilla and beat until smooth. Mix in the melted butter/chocolate mixture. Finally, add the flour and salt. Stir until combined
Line a 9×13 baking pan with parchment paper.
Pour in the batter and sprinkle remaining white chocolate chips over the top.
Bake for 30-35 minutes, until a toothpick comes out clean. Allow to cool before cutting.