Preheat oven to 350°F. Line a 9x13 pan with parchment paper and set aside.
Brown the butter: In a stainless steel skillet over medium heat, melt the butter. Swirl the pan occasionally to help the butter melt evenly. The butter will begin to foam, and then the foam will begin to subside and you’ll start to see tiny specks at the bottom of the pan, stir with a heat resistant spatula or wooden spoon and constantly stir and scrape so milk solids that are browning don’t stick. (These are what give brown butter it’s yummy flavor.) As soon as the butter turns chestnut brown and omits a nutty aroma, remove the pan from the heat and scrape the brown butter and all of the delish brown bits into a heat proof bowl. It’s important to remove to a bowl immediately so the residual heat from the pan doesn’t burn the butter. Whisk in the vanilla bean paste (if using) and set aside to cool.
12 Tbsp. unsalted butter, 1 Tbsp. vanilla bean paste (optional)
Whisk together the flour, baking powder and salt in a medium sized bowl.
2 cups all purpose-flour, 2 1/2 tsp. baking powder, 1 tsp. salt
In a large bowl, combine the slightly cooled brown butter and brown sugar.
2 cup light brown sugar, packed
Beat in eggs, one at a time, beating well after each addition.
2 large eggs
Add in vanilla and stir until combined. Gradually stir in flour mixture. Batter will be quite thick.
2 tsp. vanilla extract
Spread batter into prepared pan into an even layer. Sprinkle chocolate chips on top and bake for ~23-25 minutes. Edges should look browned and middle slightly underdone (but will continue to cook as it cools).
3/4 cup milk chocolate chips
Sprinkle with flaky sea salt on top and once cooled, cut into diagonal bars or squares. Be sure to use a clean, sharp knife and clean the knife in between cuts to get pretty bars!
flaky sea salt