This is chocolate pudding by another name, but somehow it sounds better in Italian. But frankly, language is irrelevant here: we're talking pure, all-encompassing bliss. When you eat it cooled, it is like chocolate satin cream and almost shocking in its pleasurable intensity, but I love it, too, hot and straight out of the pan when it is like the best hot chocolate you've ever had, in spoonable form.
Put the kettle on, and warm the milk and cream together either in a saucepan or microwave.
Put the sugar and cornstarch into another saucepan and sieve in the cocoa. Add the 2 tablespoons of boiling water and whisk to a paste.
Then whisk in the egg yolks, 1 at a time, followed by the warmed milk and cream, and then the vanilla extract.
Scrape down the sides of your pan and put it on the heat, cooking and whisking for about 3 to 4 minutes until the mixture thickens - if it helps, think of consistency like mayonnaise.
Take off the heat and whisk in the finely chopped chocolate, before pouring into 4 small cups or glasses each with a yield of about 2/3 of a cup.
Cover the tops of the cups with clingfilm/clingwrap (plastic wrap) to stop them from forming a skin, and then refrigerate once they are cooler. Make sure they are not still fridge-cold when you serve them. You can add a blob of cream on top if you like.