First, preheat oven to 350 degrees Fahrenheit. Line an 8 inch square pan with parchment paper.
Brown your butter. Add the butter to a skillet over medium heat. Cook, stirring occasionally, until it has reached a caramel color. Remove from heat.
Add the 1 cup of chocolate chips to this skillet. Stir until the chocolate has melted.
In a mixing bowl, add eggs and sugar. Whisk vigorously for 2 to 3 minutes, until light and frothy.
Add the melted chocolate mixture to the mixing bowl. Stir to combine.
Then, add in dark cocoa powder, vanilla, flour and espresso powder. Stir to combine.
Fold in the second cup of dark chocolate chips.
Pour batter into the lined pan. Smooth out into one even layer.
Bake for 25 to 28 minutes or until toothpick inserted comes out mostly clean.
Finally, remove from oven. Allow brownies to cool before slicing into.
