In a medium-sized bowl, whisk together the flour, cocoa powder and salt. Set aside.
Melt together the butter and powdered sugar until the powdered sugar is completely dissolved in the butter.
Whip the eggs by themselves until they are a paler yellow color and foamy.
Pour the butter/sugar mixture into the eggs and whip for two minutes. Add the vanilla extract & coffee mixture (optional) and mix until combined.
Add the flour, cocoa powder and salt and fold together until a batter forms.
Pour the batter into an 8x8 inch pan and bake for 40-45 minutes at 350 degrees Fahrenheit.Let cool in the pan, slice & enjoy!