Preheat the oven to 355°F (180°C), gas mark 4.
Grease and line two 9-inch (23 cm) loose-bottomed cake pans or one deep 9-inch (23 cm) springform cake pan
In a large mixing bowl, whisk together the flour, the superfine sugar, cocoa, baking powder, baking soda, and sea salt.
In a large measuring jug, whisk together the oil, milk, yogurt, eggs, and vanilla.
Pour the wet mixture into the dry ingredients and mix together. Fold in the hot coffee and divide between the pans/ or pour into one pan.
If baking 2 cakes, bake for around 25 minutes. If baking 1 large cake, bake for around 35 minutes. Check the sponge with a skewer or toothpick to make sure it is cooked all the way through. Leave to cool in the pans for 10 minutes, then transfer to a wire rack to cool completely. Then decorate however you like.