Preheat the oven to 160c regular bake.

Grease a 20-22cm cake tin and dust all over with cocoa.

Sift the flour, sugar, cocoa, baking soda and salt into a large mixing bowl.

Stir with a whisk to combine evenly and make a large well in the centre.

Pour the olive oil, vinegar, vanilla and water into the well.

Using the whisk, stir the mixture gently in a circular motion until combined to a smooth batter.

Bake just below the centre of the oven for about 50 minutes, or until a toothpick inserted in the middle comes out clean.

Let the cake cool in the tin for 10 minutes before turning it out onto a rack.

Dust with icing sugar to serve or ice it when cool.

For a delicious pudding, dust with icing sugar and serve hot with ice cream.

To make the chocolate icing, place the chopped chocolate and butter (or coconut cream) in a heatproof bowl over simmering water.

Stir until melted, then remove from heat and stir in the oil.

Leave to cool at room temperature until thick enough to spread on the cake.