Preheat the oven to 180 C / Gas 4. Grease a 20cm cake tin and line with baking parchment.
In a mixing bowl, cream the butter and sugar together then gradually beat in the eggs, one at a time, until the mixture becomes smooth.
Sift in half of the flour and fold. Gradually add the milk then sift in the rest of the flour and fold into the mixture. Mix the water and oil in, then the cinnamon, salt, and vanilla. Stir in the chocolate chunks. Transfer to the prepared cake tin.
Bake in the preheated oven for 1 to 1 1/2 hours, or until a skewer inserted into the cake comes out clean. Remove from the oven and allow to cool, about 90 minutes, fully then remove from the tin.
For the ganache:
Place the chocolate into a bowl. Gently heat the cream, then pour over the chocolate and stir until smooth. Stir in the salt. Leave the ganache to cool to a spreadable consistency (you can place briefly in the freezer to help the process along). Spread or pipe over the cake. Slice and serve, now, time to indulge!
I sometimes serve this cake whilst it's still warm, and pour on the unset ganache like a sauce with a nice big dollop of creamy ice cream. However, is just as good cool, and drenched in pouring cream! I always serve this with a pot of tea.