Pre-heat the oven to 160C(320F) fan-forced and spray a 24cm spring-form tin with oil.

Wrap the entire outside of the pan with three layers of aluminum foil. I used 4 just to be sure. Make sure it wraps around the bottom and up to the rim of the tin.

Place the water and sugar in a small saucepan and bring it to boil over medium heat, stirring constantly until the sugar has dissolved.

Reduce the pot to a simmer and heat it for a further 5 minutes then remove the pot from the heat.

In another saucepan, melt the butter then add the chocolate and whisk it in until the mixture it smooth and the chocolate has melted.

Pour in the sugar/water mixture and whisk it until it is incorporated into the chocolate.

Leave it to cool slightly and then whisk in the eggs.

Pour the batter into the tin and place the tin in a baking pan.

Pour hot water into the baking pan until it reaches half way up the sides of the cake tin.

Bake the cake inside the baking pan for 45-50 minutes or until there is no more jiggle in the middle when you shake the tin.

Very very carefully remove it from the oven. Take the tin out of the water bath and leave it on a wire rack to cool completely in the tin.

To make the ganache, heat the cream in a large heat-proof bowl in the microwave, 30 seconds at a time, until it starts to bubble. Add the chocolate and whisk it into the cream until it has all melted.

Top it over the cake and spread it out so the top is flat.

Transfer the cake to the fridge to set for at least 2 hours.

This cake can be made up to two days in advance and kept covered in the fridge.