Preheat oven to 350F/176C. Grease an 8″x 8″ pan and line with parchment paper.
In a small saucepan on very low heat or a double boiler, melt butter with chocolate, oil, two tablespoons of the cocoa powder, instant coffee and salt. Stir until completely melted and smooth. Set aside to cool.
In a large bowl beat eggs with an electric mixer on high speed. Add sugar gradually and beat until thick and pale, 3-4 minutes. Add brown sugar and beat until well blended. Add vanilla.
Gradually beat in cooled chocolate mixture (it should not be warmer than blood temperature). Blend until smooth, scraping down sides of bowl as necessary. Sift in flour and remaining two tablespoons of cocoa powder and fold in. Add mix-ins before flour and cocoa are fully incorporated. Mix only until all traces of flour have disappeared; do not over mix.
Spread batter evenly into prepared pan, patting down with fingers or spatula if necessary. Bake for exactly 20 minutes. Edges should be slightly puffy. Remove from oven and slam pan a few times. Allow to cool completely before cutting into squares.