Preheat the oven at 160ºC/320ºF conventional oven and prepare a loaf pan with parchment paper.
Sift together the all-purpose flour, cocoa powder, espresso powder, baking powder and salt and set it aside.
170 g all-purpose flour, 70 g dutch process cocoa powder, 1 ½ teaspoon espresso powder, ½ + ¼ teaspoon baking powder, 1 teaspoon salt
In a mixing bowl, use the paddle attachment, add the butter and granulated sugar and mix it on high speed for 3 minutes.
200 g butter, 350 g granulated sugar
Scape down the sides of the bowl and add the eggs one at a time and mix them in until combined. Add the vanilla extract and mix it in.
4 eggs, 1 ½ teaspoon vanilla extract
Continue by adding ½ of the flour mixture and mix it in. Then add the sour cream and mix it in. Then add the other ½ of the flour mixture and give it a final mix until just combined. Scape down the sides of the bowl with a spatula to make sure all the ingredients have been incorporated.
200 g sour cream
Pour the cake batter into the prepared loaf pan. Take a butter knife and insert it into the top of the batter in the loaf pan and run it a straight line down the middle of the batter. This way the pound cake gets a perfect crack in the middle. Bake it for 1 hour and 25-30 minutes.
Let the cake cool on a cooling rack. After 10 min, gently remove the cake from the cake tin and let it cool down completely.