Preheat oven to 160C fan/180C/325F/Gas 3. Grease two non-stick, 7 inch cake tins and set aside.
Add self-raising flour, baking powder and instant coffee to a medium bowl and mix until well combined.
Next, add unsalted butter and brown sugar to a large bowl. Then, whisk for 3-5 minutes.
Pour one egg into the bowl and whisk until it disappears. Repeat this step for the remaining eggs.
Add half of the dry ingredients into the egg mix and pour in a splash of milk and mix for a minute. Repeat this step for the remaining dry ingredients and mix until well combined.
Pour cake batter into the greased tins and bake for 25 minutes or until done. Remove cakes from tins and leave to cool upside down.