Mix the espresso with the cream, the sugar and the milk. Bring this to a simmer.
While that’s heating up mix the egg yolk with the cornstarch. Mix it well till there are no more lumps.
Once the liquid is simmering while stirring add it to the yolk mixture. Sometimes there’s even already enough heat to cook the cremeux, so then you don’t need to pour it back into the pan and give it more heat.
Now add the dark chocolate and blend it till smooth. Do this with a hand blender to get a beautiful and shiny emulsion.
Then cover it and let it cool down completely. This will take a couple of hours. Once cold transfer it into a piping bag and keep it in your fridge.
