In a heavy based saucepan over medium high heat combine cream, milk and vanilla extract.
Heat until steaming or just below boiling point, whilst stirring constantly.
In a separate bowl combine egg yolks and sugar and whisk until light and fully incorporated.
Whist stirring the egg mix slowly pour in 1/3 of the cream mix to temper the eggs. once combined slowly add the remaining cream mix whilst stirring.
Turn the heat to medium low and add the egg/ cream mix back into the saucepan and onto the reduced heat.
With a wooden spoon stir until the mix is thick, but not letting the heat above 84C. There should be ribbons following the spoon when stirring.
Remove from heat and add the chocolate, stirring constantly to avoid scolding the chocolate. Stir until the chocolate has melted. (if the chocolate is being stubborn, add it to a very low heat whist stirring until the chocolate is fully melted)
Have cups, jars, little bowls ready to pour your custard mix into. Fill, let cool to room temperature then transfer to fridge until set (at least 4 hours)
To serve remove from fridge 10 minutes before to soften slightly, garnish and enjoy.