- Grease an 8x8 pan. For easy removal of the brownies, place parchment paper on the bottom and 2 sides of the pan. Grease again and then set aside. 
- Into a cup, add milk and vinegar. Allow it to sit on the counter for 5-10 minutes to activate while you prep the rest of your ingredients. - 1/2 cup milk, 1 tsp white vinegar 
- In a medium bowl, whisk the hot melted butter and sugars. Whisk for 2-3 minutes until the mixture is homogenous and not oily on the sides. - 3/4 cups butter, 3/4 cups light brown sugar, 1/2 cup white sugar 
- Whisk in the milk mixture. This has to be smooth in order for the brownies to turn out good. If it's clumpy, place into the microwave or use a double boiler method and heat for 2-3 minutes. Then continue whisking until smooth. 
- Whisk in the cocoa powder until well combined. - 1/2 cup unsweetened cocoa powder 
- Mix in the flour, baking powder, cornstarch, and salt until no dry streaks are showing. Mix in chocolate chips. - 1 cup all-purpose flour, 1 tbsp cornstarch, 1/2 tsp baking powder, 1/4 tsp salt, 1/2 cup semi-sweet chocolate chips 
- Transfer the batter into the prepared 8x8 pan and spread evenly. Top with extra chocolate chips.  
- Bake the brownies for 45-55 minutes at 350℉. Bake until a toothpick inserted into the batter (not chocolate chip) is fudgy and not batter-like. You'll know it's ready when you move the brownie pan and the center of it doesn't jiggle. 
- Cool, slice, and enjoy!