Preheat your oven to 180°C (350°F) or 160°C (325°F) for a fan-forced oven.
Mix together your dry ingredients (flour, cornstarch, cocoa powder, instant coffee, baking powder and salt) and whisk to combine well.
Mix the oil, egg white and yoghurt together in a small bowl.
Add a well in the center of the dry ingredients and add your wet ingredients in the middle and whisk until just combined.
Pour the batter into your prepared pans and bake for about 18minutes or until a toothpick comes out clean or the sides of the cake has pulled away from the sides of the pan.
Allow to cool in the pan for a few minutes before turning out onto a wired rack to cool.
If you baked thicker layers cut the layers in half with a serrated knife rotating as you cut to ensure you cut the layers evenly. If you used a larger pan, cut out rounds from the layers and stack to make two mini cakes.