Preheat the oven to 325°F (165°C) and place an 8-inch (20cm) round cake pan in a large roasting pan and set aside. Set a kettle of water to boil.

Make the Caramel Topping In a small, heavy bottomed saucepan, add one cup (8 oz/225 g) of sugar and ¼ cup (2 fl oz/60 ml) water and turn the heat on to medium low. Stir gently until the sugar is dissolved, then stop stirring. Allow to simmer gently and watch carefully until the sugar caramelizes to a deep, dark amber color, about 8-10 minutes. Immediately remove from the heat and pour into your 8-inch (20 cm) cake pan and let cool until hardened.

Make the Chocolate Custard In a medium, heatproof bowl, whisk the egg yolks with the remaining ¼ cup (2 oz/57 g) of sugar and set aside. In a medium, heavy bottomed saucepan over medium heat, warm the milk, cream, chocolate, cinnamon, cayenne pepper and salt until the chocolate has melted. Remove from the heat. Gradually pour this hot liquid into the egg yolks while whisking constantly. Strain the custard through a fine mesh sieve into the cake pan on top of the hardened caramel.

Place in the oven and pour boiling water from the kettle into the roasting dish to come halfway up the sides of the cake pan. Bake for about 50 minutes, until the edges are set but the center is still jiggly.

Remove from the water bath and let cool to room temperature before transferring to the refrigerator for at least 4 hours or overnight to set.

When ready to serve, loosen the edges of the flan by running a thin knife all around the edge of the custard. Place a rimmed serving plate on top of the pan, then invert onto the plate. Gently remove the cake pan and serve immediately.