Place the pot over medium-low heat and cook, whisking quite rigorously constantly, making sure you scrape the sides of the pot from time to time. Cook until the mixture starts to simmer - bubbles will start popping from the surface. Remove the pot from heat and dip a metal spoon or spatula into the mixture - the mixture should be thick enough to coat the back of the spoon or spatula. If it's not thick enough, continue cooking the mixture, whisking constantly, until the mixture thickens.
Once the mixture has thickened, remove from heat and add in all the chocolate. Whisk until the chocolate has melted and the mixture is smooth. Whisk in the vanilla and Baileys. If there are lumps, strain the mixture through a sieve.
Divide the pudding between two ramekins. Place a plastic wrap directly onto the surface of the pudding to prevent a skin from forming. Chill the pudding the refrigerator for at least 4 hours. The pudding can be kept in the refrigerator for up to 3 days.
To serve, remove the plastic wrap, decorate with chocolate shavings or whipped cream and serve chilled.
Chocolate shavings or whipped cream
The chocolate pudding can be easily scaled up to serve more people. Do note that the more you make, the longer time you will need to cook the pudding until it thickens.
If you don't want to add Baileys, use 230 grams of milk instead of 200 grams.
The chocolate can be replaced with a mix of semisweet, plain or milk chocolate.