Preheat oven to 350 degrees. In a mixing bowl, whisk together flour, cocoa powder, baking powder, and salt. Set aside.
In a separate mixing bowl, using a wooden spoon, mix together granulated sugar, light-brown sugar, and melted butter until combined.
Stir in eggs and vanilla extract and mix until blended. Add half of the flour mixture and mix just until combined, add in milk and mix just until combined, then add the remaining flour mixture and mix just until completely combined (batter will be very thick).
Pour batter into a greased 8x8-inch square baking dish and spread into an even layer.
Bake in preheated oven for 25 to 30 minutes until the center is nearly set. Allow time to cool completely then frost with Chocolate Cream Cheese Frosting and cut into squares (the frosting is a must for this recipe).
Chocolate Cream Cheese Frosting - In a mixing bowl, using an electric hand mixer on medium speed, whip together the cream cheese and butter until smooth and fluffy, about 1 minute. Add in vanilla and powdered sugar, then sift in cocoa powder and mix until smooth and fluffy, about 1 minute.
*If you want a stronger chocolate flavor, you can use ½ cup cocoa powder instead of the ⅓ cup listed. I just wanted a milder chocolate flavor for this brownie so I like ⅓ cup, but I have tested out both. If you do add ½ cup cocoa then reduce the flour measurement by 2 ½ Tbsp. Enjoy!