Preheat the oven to 175 C. Grease a 9" round cake tin (preferably springform for easy removal) and set aside.
Sift the flour, cocoa, baking powder and salt together in a bowl. Set aside.
In a mixing bowl, whisk the sugars and olive oil till well combined.
Now add the hot water slowly, alternating with the flour mixture. Stir to make a smooth batter.
Pour into the prepared tin and bake for 40 to 45 minutes until a toothpick poked in the center comes out clean. Start checking for doneness at 30 minutes. The cake doesn't rise very tall and the surface stays quite flat.
Allow the cake to cool at room temperature while you make the frosting.
Place the chopped chocolate in a bowl. Heat the cream and bring it to a gentle simmer, then pour immediately over the chocolate. Let it sit for a few minutes, then stir to combine into a smooth, runny ganache. Keep in the refrigerator for 1 hour, or until it is completely chilled.
Stir the powdered sugar into the ganache, then whip with a hand mixer until it becomes pale, thick and forms soft peaks.
Spread the frosting over the top of the cake and over the sides if you wish. Decorate with shaved chocolate or sprinkles! If not serving immediately, store the cake in the fridge. Bring to room temperature before slicing. The unfrosted cake will last about a week in the fridge and 3 to 4 days after frosting. Happy baking!