Preheat oven to 350. Butter an 8x8 or 9x9 square pan. Alternately, you can line the pan with foil, leaving a couple inches of overhang on two sides (this will allow you to lift the whole tray of brownies out of the pan for easy removal). If using the foil, butter or spray it.

In a large bowl combine cocoa powder, sugars, salt, flour, espresso powder and chocolate chips. Whisk until combined. Add eggs, oil and water or coffee and stir until combined.

Pour the batter into the prepared pan and smooth the top. Bake for 30-40 minutes (begin checking at 30 minutes). The brownies are done when a toothpick inserted into the center comes out without raw batter on it (there may be some fudgy crumbs on the toothpick - that's ok). Be careful not to over bake. Remove from the oven and place on a cooling rack. Cool completely.

Beat powdered sugar and butter with a hand mixer or stand mixer until smooth. In a separate bowl stir together the cream, espresso powder and vanilla extract. Pour into the butter/sugar mixture and beat on medium speed for several minutes, until smooth and creamy, scraping down the sides of the bowl as necessary. Using a butter knife or offset spatula, evenly spread the espresso buttercream over the top of the brownies. Place the brownies in the fridge while you prepare the ganache.

In a small saucepan over medium-low heat, combine the cream and chocolate chips. Stir until melted and smooth. Remove from the heat and allow to cool slightly, for a couple of minutes. Pour the ganache over the buttercream topped brownies, smoothing the top. Return to the fridge for at least an hour for the ganache to firm up