1. Preheat the oven to 160°C.

2. Line the base of a large baking dish with a tea towel, folded to fit.

3. Place the sugar and water in a medium saucepan over low a heat. Cook, stirring constantly, for 5 minutes or until the sugar is dissolved.

4. Increase the heat to medium and bring to the boil. Cook, without stirring, occasionally brushing down the side of pan with a pastry brush dipped in water for 7 minutes or until golden. Use a tea towel or oven mitt to hold a round 20cm cake pan with one hand. Pour in the caramel and swirl to coat the base and 2cm up the side. Set aside to cool.

5. Place the milk and chocolate in a medium saucepan over low heat. Cook, stirring, for 4-5 minutes or until the chocolate has melted and the mixture is smooth.

6. Whisk together the eggs, condensed milk, cinnamon and vanilla in a large bowl. Gradually add the chocolate mixture to the egg mixture, whisking constantly. Place the cake pan in the lined baking dish. Pour the custard mixture into the pan. Pour enough boiling water into the dish to come halfway up the side of the pan. Bake in oven for 40 minutes or until just set.

7. Carefully remove the cake pan from the baking dish. Set aside for 45 minutes to cool. Place in the fridge for 8 hours or overnight to chill.

8. To serve, run a flat-bladed knife around the edge of the pan. Carefully turn the flan onto a serving plate. Cut into wedges and serve with grated trade aid dark chocolate on top to garnish.