
When you're making a classic blondie, browning the butter for its nutty flavor is a must, as is using white chocolate chips and walnuts.
Preheat oven to 350º. Line an 8"-x-8" pan with parchment paper and grease with cooking spray.
In a small saucepan over medium heat, melt butter. Cook, swirling pan occasionally, until deep golden bits collect on bottom of pan and butter smells nutty. Remove from heat immediately and let cool slightly.
In a large bowl, whisk together browned butter and sugars. Stir in egg, vanilla, and salt, then add flour, stirring until just combined. Fold in white chocolate chips and walnuts.
Press batter into prepared pan and smooth top. Bake until golden around edges and a toothpick inserted until center comes out with a few moist crumbs attached, 20 to 25 minutes.
Let cool completely before slicing into squares and serving with ice cream and caramel, if desired.