• Preheat the oven to 325 °F. Grease a 9x5 inch metal loaf pan and line with a rectangle of parchment paper for easy removal.
• In a small saucepan, bring ½ cup of the water to a boil. Remove from heat and stir in the chopped chocolate. Let stand until the chocolate softens. Stir until melted and smooth, then stir in the espresso powder and remaining ½ cup of water (total liquid 1 cup). Stir in 2 tablespoons of vegetable oil.
• Sift the flour, then whisk together with baking soda, baking powder and salt. Set aside.
• Using an electric mixer, beat the butter until creamy. Add the brown sugar and continue beating for about 3 minutes on medium high, scraping down the bowl as needed.
• Beat in the eggs one at a time, mixing for about 30 seconds after each. Then beat in the vanilla extract.
• Add the sour cream to the chocolate mixture and just give it a little stir. No need to completely blend it, as it will all come together.
• Add the chocolate mixture and dry flour mixture alternately in 3 parts, stirring or beating on low speed with the paddle until everything is well mixed.
• Pour the batter into the prepared pan. Bake on the center rack at 325 °F for one hour and 15 minutes or until a toothpick inserted in the middle comes out clean. I recommend checking at 1 hour, as the shape and material of your loaf pan (and oven) could affect the time.
• Let the cake cool in the pan for about 15 minutes. Then invert the loaf onto a wire rack to cool completely.

Frosting

• Sift together the powered sugar and the cocoa powder and set aside. Sifting is an extra step, but it can really help make icing smoother and creamier. Beat together softened butter and half of the powdered sugar mixture until smooth. Add salt, sour cream, vanilla and remaining powdered sugar, beating until mixed, then add milk as needed, beating and scraping side of bowl until smooth and fluffy.