Preheat the oven to 170c fan

Grease and line a 9 inch cake tin

In a small bowl stir together the boiling water,cocoa powder and the coffee. Whisk it well until glossy and set aside.

In a large bowl sift in the flour, sugar, baking powder, bicarbonate of soda and the salt. Add the egg, yoghurt and the vegetable oil. Give it all a good mix and then stir in the little bowl of chocolate you prepared earlier.

Pour the batter into your prepared cake tin and bake for about 20-25minutes until it springs back to touch.

Leave to cool for 5 minutes before turning out on to a rack to cool completely.

Once the cake has cooled, I then wrap a strip of baking parchment around the inside of the cake tin - to add an inch or so to the top of the cake tin - like a collar - just as an insurance policy to make sure we have room for the mousse -  and then pop the cake back into the tin.

For the chocolate mousse. Place the chocolate in a glass bowl and melt over gently simmering water. Or do it in the microwave in 30 second bursts. It's important not to let the chocolate get too hot or is will burn. Once melted, set aside to cool.

Whip the cream until it forms soft peaks. Then gently fold in the melted chocolate until no streaks are left. Spoon this over the chocolate cake and smooth out and pop it in the fridge to set for at least 4 hours but this is most easily done overnight.

When the mousse has set remove the cake from the tin and peel off the baking parchment collar. Place on a serving plate.

For the ganache, place the chopped chocolate in a bowl. Heat the cream in a small pan over a medium heat until it just begins to gently simmer and then turn the heat off and pour the cream over the chocolate. Let it sit for 2 minutes and then stir gently to encourage the remaining chocolate to melt and it's all nicely combined.

Pour the ganache over the centre of the cake and use a spoon to spread it over the top, allowing it to drip down the sides.

Chill the cake for 30 mins to allow the ganache to set.

I like mine topped with little dollops of whipped cream, berries and edible flowers and a sprinkle more flakey sea salt.