1 Line a bottomless 10-inch cake tin (springform) with 4 layers of cling film so it reaches the corners of the tin and is watertight. Rub with a little oil.
2 Heat the oven to 170C/Gas Mark 3 and whisk the eggs with 60g of sugar until very voluminous.
3 Mix 60g of sugar and the water in a pot and heat on the hob until it reaches a syrup consistency. This should take a couple of minutes. Remove and add the chocolate and soft butter and combine with a whisk.
4 Add the chocolate mix to the whisked egg, and using a whisk, mix together to create the cake mix.
5 Add this mix to the prepared tin and cook in a water bath with a tight tin foil lid on for 45 minutes to 1 hour. Remove from the oven and leave to cool to room temperature.
6 To make the caramel sauce, melt 200g of sugar in a thick-bottomed pot until it’s quite dark and brown. This will take a few minutes and don’t be tempted to stir it too much or it may crystallize. And never leave boiling sugar unattended. Then remove it from the heat and allow it to cool slightly before whisking in the cream. Add a pinch of salt and pass through a sieve and into a serving jug.
7 When ready to serve the nemesis, remove it from the tin by placing a plate, or board, on top of the tin (foil removed) and turning it upside down so the cake falls out. Cut into portions using a very clean, hot knife. Clean the knife in hot water after every cut and serve with the caramel sauce and either some ice cream or crème fraîche.