Preheat oven to 325°F/160°C. Grease an 8½ x 4¼-inch loaf pan.
In a medium bowl, sift together flour, cocoa powder, baking powder, and salt.
In a small bowl combine milk and coffee.
Using a mixer fitted with the paddle attachment, beat butter and sugar on medium speed for 3 minutes until fluffy. Occasionally scrape down the sides and bottom of the bowl. Add eggs and vanilla extract and beat until combined. On low speed, beat in flour mixture in 3 additions, alternating with the milk mixture in 2 additions, starting and ending with the flour. Once all is added, be careful not to overmix the batter.
Scrape batter into prepared pan and smooth the top. Bake for 45-60 minutes or until a skewer inserted into the center of the cake comes out dry. If the cake is browning too much while baking, cover the top loosely with aluminium foil. Remove from oven and allow to cool completely on a wire rack. Serve cake at room temperature. The coffee flavor gets stronger over time, after about 24 hours.
Store cake in an airtight container in the refrigerator for up to 5 days. Cake can be frozen for up to 2 months. Thaw overnight in the fridge.