Preheat the oven to 350 degrees F (180 degrees C). Line a 9×9-inch pan baking pan with parchment paper.
Place Unsalted Butter (1 cup) in a saucepan and bring to a bubble over medium heat. Let the butter gently bubble, swirling the pan occasionally, until the mixture smells nutty and starts turning brown, then quickly remove from heat and transfer to a bowl. The whole process should take about 10 minutes. Let cool before using.
In a medium bowl, whisk the All-Purpose Flour (2 cup), Baking Powder (1 teaspoon), Baking Soda (1/4 teaspoon) and Maldon® Sea Salt Flakes (1 teaspoon) and set aside.
In a separate bowl, beat the Egg (2). Whisk in the Brown Sugar (1 1/2 cup), browned butter, and Vanilla Extract (1 1/2 teaspoon) and mix until smooth.
Add the dry ingredients to the wet and stir together until just combined. Stir in your White Chocolate (2/3 cup) or mix-ins of choice.
Bake until a toothpick inserted in the center comes out clean, about 30 – 35 minutes.
Cut into squares and serve!