Brown the butter. Place butter pieces in a light-colored pan. Bring to medium heat and stir constantly with a rubber spatula or gently swirl the pan. Keep the butter moving so it melts evenly and doesn’t burn. The butter will melt, then it will start to foam up. The foam will subside and the butter will start to brown. Once you see little brown flecks and the butter has a nutty aroma, remove it from the heat and immediately transfer to a heatproof bowl. Set aside to cool slightly.

Dry the pumpkin purée. Use a few paper towels to pat any excess moisture out of the pumpkin purée. This step is odd, but it helps prevent a cakey texture. I find it helpful to work just a spoonful or two at a time.

Whisk the dry ingredients. In a large bowl, whisk together the flour, baking soda, salt and pumpkin pie spice. Set aside.

Beat the wet ingredients. Add the brown butter, brown sugar, egg, egg yolk, pumpkin and vanilla to the bowl of a stand mixer. Mix on medium-high speed until well combined.

Add the dry ingredients to the wet ingredients. Use a spatula to mix just until combined. Stir in the white chocolate chips.

Transfer batter to prepared pan. Bake for 25 to 28 minutes or until a toothpick inserted in the center comes out with little to no crumbs. Cool completely before cutting and serving.