Preheat the oven to 350°F / 175°C. Grease and line a 8" square pan with butter and parchment paper.
In a medium saucepan set over medium heat, melt together the butter and chocolate. Turn off the heat, then immediately whisk in the cocoa powder and instant espresso.
In a medium sized mixing bowl, use a hand mixer or stand mixer fitted with the whisk attachment to beat together the eggs and sugar for 4 minutes.
Slowly whisk the melted chocolate mixture into the egg mixture.
Add in the flour and salt. Whisk together just until no flour streaks remain.
Pour the brownie batter into the prepared pan. Bake for approximately 30 minutes, or until the brownies are set on the outsides and only slightly jiggle in the middle.
Wait for the brownies to fully cool before cutting. Serve, and enjoy!