Preheat your oven to 350 degrees F.
Prepare a 9 x 13 inch baking pan by spraying it with nonstick spray and covering the bottom with parchment paper. Make sure to leave some parchment paper hanging out of the pan. This will allow you to lift it out seamlessly. Set the pan aside.
In a large bowl, fully whisk together the butter and brown sugar until it is soft and pale.
Add in the vanilla extract, egg, and egg white. Whisk again to combine.
Over the top of the egg and butter mixture, add the flour, baking powder, baking soda, and salt. Gently whisk the dry ingredients together before whisking them into the bottom wet batter.
Stir until everything just combines. Do not over mix.
Add in the raspberries, ripping them in half with your hands (or cutting them with a knife), and the white chocolate chips. Gently fold both into the batter so the raspberries don’t get too mushy.
Scoop the batter into the prepared pan. Top with additional raspberries and white chocolate chips. Then, place the pan into the oven for 25 to 30 minutes or until a toothpick inserted in the middle comes out clean.
Remove the pan from the oven and allow it to cool for about 5 minutes. After 5 minutes, carefully lift the blondies out of the pan using the overhanging parchment paper and place them on a wire cooling rack. Allow them to cool completely before slicing and serving.
OPTIONAL: Melt additional white chocolate chips in a plastic zip top bag, cut a small corner of the bag and drizzle the melted chocolate over the cooled blondies. Allow the chocolate to harden, then serve and enjoy.