Preheat your oven to 350°F.
Spray a 9-inch square pan with baking spray or lightly butter and dust with cocoa powder, making sure to tap out any excess cocoa.
In the bowl of a stand mixer fitted with the paddle attachment, combine melted butter (1/2 cup), white sugar (1/2 cup) and brown sugar (1/2 cup). This can also be done using a standard bowl and whisk.
Once combined, add in eggs (2) and vanilla extract (1 tsp) and beat until it becomes smooth and pale yellow. I recommend speed #4 for 2-3 minutes.
Add in flour (3/4 cup), cocoa powder (1/2 cup), salt (1/2 tsp), and instant espresso powder (1 tbsp). Mix just until no lumps of flour remain.
Pour into greased pan and bake on the center rack for 25-30 minutes. The middle should be set (doesn’t jiggle when you shake the pan) but a toothpick may not come out completely clean— these are really fudgy brownies. Allow the brownies to cool completely before icing.