Preheat oven to 350°F. Line a 9x13-inch baking pan with parchment paper, leaving paper hanging over the sides of the pan so that you can easily remove the blondies from the pan later.
In a large mixing bowl, whisk together the melted butter, brown sugar, and granulated sugar until well combined. The mixture should be paste-like and cleanly pull from the sides of the bowl when it is finished.
Whisk in the eggs and 1 yolk, vanilla and almond extract, just until combined.
Add flour, cornstarch, baking powder, and salt to the wet ingredients, mixing until just combined. Be careful not to overmix.
Gently fold in the white chocolate until evenly distributed in the batter.
Pour the batter into the prepared baking pan and spread it out evenly with a spatula.
Scatter the raspberries evenly over the top of the batter, gently pressing them down slightly into the batter.
Bake in the preheated oven for 34-38 minutes, or until the blondies are golden brown around the edges and a toothpick inserted into the center comes out with a few moist crumbs.
Remove the pan from the oven and allow the blondies to cool completely in the pan on a wire rack.
Once cooled, use a sharp knife to cut the blondies into squares or bars.