Preheat oven to 350 degrees F. Line a 9x13 inch metal pan with nonstick foil.

In a mixing bowl, whisk together the cocoa, espresso powder, and boiling water until smooth.

Add the unsweetened chocolate and stir until melted. Stir in the oil and melted butter. (Mixture may look curdled.) Add eggs, yolks, and vanilla and continue to whisk until smooth.

Whisk in sugar until fully incorporated. Add flour and salt and mix with rubber spatula until combined. Fold in chocolate chips (or chopped chocolate).

Scrape batter into pan and bake for about 30 to 35 minutes.

Let cool for about 10 minutes, then grasp foil, lift from pan and let cool completely.