Preheat your oven to 175°C (350°F). Line a 20 cm (8-inch) round cake pan with parchment paper and lightly grease it.

In a large bowl, sift together the flour, cocoa powder, baking powder, and salt.

In another bowl, cream the softened butter and sugar using a mixer on medium speed until light and fluffy (about 3 minutes).

Add eggs to the butter-sugar mixture one at a time, beating well after each addition. Mix in vanilla extract.

In a separate jug, combine the brewed espresso and milk.

Add half of the flour mixture to the creamed mixture and mix on low speed until just combined. Pour in the espresso-milk mixture and blend gently. Add remaining flour mixture and mix until the batter is smooth.

Pour the batter into the prepared cake pan. Smooth the top with a spatula.

Bake for 28-32 minutes, or until a skewer inserted in the center comes out clean.

Cool in the pan for 10 minutes, then transfer to a cooling rack to cool completely before serving or frosting.