Preheat the oven to 350°F. Grease an 8x8-inch baking dish with some of the extra butter and line it with parchment paper, leaving an overhang to lift the blondies out after baking.

Place the ¾ cup (1½ sticks) unsalted butter, sliced into pats, in a light-colored saucepan and melt over medium heat.

Stir the butter constantly as it cooks. The butter will foam, then the foam will subside; continue cooking, stirring, for about 5 to 10 minutes, until the milk solids at the bottom turn golden brown and the butter smells nutty.

Remove the pan from the heat and immediately pour the browned butter into a large heatproof bowl to stop the cooking. Allow the butter to cool slightly until it is warm (not hot) to the touch.

Add the 1½ cups light or dark brown sugar, the 2 large eggs, the 1 large egg yolk, and the 1 tablespoon vanilla extract to the warm browned butter. Whisk until smooth and well combined.

Sprinkle the 1 teaspoon sea salt over the mixture and whisk briefly to incorporate.

Add the 1½ cups all-purpose flour (spooned and leveled) to the bowl. Use a spatula to fold and stir the batter until the flour is just incorporated; do not overmix.

Fold in the ½ cup chopped walnuts and the ½ cup white chocolate chips, reserving some walnuts and chips to press on top if you like.

Transfer the batter to the prepared pan and spread it into an even layer. Press the reserved walnuts and white chocolate chips onto the top of the batter.

Bake for 28 to 30 minutes, or until the edges are golden brown and small cracks form on the surface.

Remove from the oven and allow the blondies to cool completely in the pan before using the parchment overhang to lift them out and slice.