• Preheat oven to 350°F. Generously grease a loaf pan. You can either flour it by adding a couple tablespoons of flour to the greased pan, tapping it around to coat the greased pan (discard excess flour from pan), OR you can line the bottom of the pan with a rectangle of parchment paper and grease it. This will help ensure the cake does not stick to the pan.
• Put cocoa powder in a small bowl, then pour hot coffee over the top. Whisk to dissolve. Set aside to cool to room temperature. Make sure you have another 1 Tablespoon of brewed coffee set aside for the glaze.
• In a large bowl, add the sugar, salt, baking soda, and egg yolk and mix on low with an electric mixer for one minute until combined. Add the buttermilk, oil, and vanilla and mix on low for another minute until combined.
• Add the flour and mix on medium speed for two minutes. Add the cooled cocoa mixture and mix on medium speed for another two minutes. Pour the batter into the prepared loaf pan. Bake for 45 minutes in preheated oven or until a cake tester/toothpick comes out clean.
• Let cake cool for at least 20 minutes in the pan, then turn it out onto a cooling rack to cool completely before topping with glaze.

Chocolate Sour Cream Glaze

• When cake is cool, place chopped chocolate and butter in a small bowl and microwave for 30 second intervals mixing after each until melted and smooth. Make sure you don't microwave more than necessary to prevent the chocolate from seizing.
• Once smooth and melted, add ¼ cup of the icing sugar and whisk to combine. Add the sour cream and whisk. Add the last ¼ cup of icing sugar and whisk until smooth and thick. Add the coffee and whisk. The glaze should become really smooth and glossy.
• Spread the glaze over the top of the cooled cake. If desired, garnish with fresh berries, shaved chocolate, or sprinkles. Cut into 4 slices and serve. Can be kept at room temperature for the day, but refrigerate if leaving overnight.