In a large frying pan over medium heat, add the butter. Let the butter melt and then, stir occasionally. It will get extra bubbly and start to turn foamy right before it browns. When it starts to get foamy and before it starts to brown, add the milk powder. It will get extra foamy. Keep stirring until the milk deposits separate and your butter turns amber in color.
1 cup Unsalted butter, 3 TBSP Dry milk powder
Add in the sifted cocoa powder and heat for 30 seconds. Pour butter into a bowl and place in the freezer for 15 minutes to cool quickly.
1 cup Unsweetened cocoa powder
Preheat the oven to 350℉. Spray a 9X9 inch square pan with baking nonstick spray. Line the bottom and two sides of the pan with parchment paper. Spray again.
In a small bowl, mix the flour, cornstarch, and salt. Set aside.
3/4 cup All-purpose flour, 1 TBSP Cornstarch, 1 tsp Salt
Using a mixer in a large mixing bowl, add sugar, powdered sugar, eggs, and egg yolk. Beat on high speed for 3 minutes.
1 cup White granulated sugar, 3/4 cup Powdered sugar, 3 Large eggs, 1 Egg yolk
Take off the mixer. Add in the cooled butter, oil, and vanilla. Mix using a baking rubber spatula. Add in the dry ingredients and mix until just combined. Add in the chocolate chips and fold it in.
2 TBSP Oil, 1 tsp Pure vanilla extract, 1 cup Semi-sweet chocolate chips
Pour the brownie batter to the prepared pan. Bake for 34-36 minutes. Bake until the edges are set but the middle is a little under done. It will finish the baking while it cools.
Cool brownies in the pan on a cooling rack. Then, remove from pan and cut into 16 squares.