Crémeux au Chocolat (Chocolate Crémeux)

Mix egg yolks with sugar until well incorporated. Bring heavy cream and milk to a simmer and slowly pour into the egg yolk mixture while whisking vigorously. When fully incorporated, transfer the yolk + milk liquid back into the pot, whisk over medium heat until the mixture slightly thickens (it should coat the back of a spoon). Pour the hot mixture onto the dark chocolate. Let it soak for 1 minute, then whisk until well incorporated and smooth. Place the crémeux in a plastic wrapper, pressing it directly onto the surface to prevent a skin from forming, and let it chill overnight in the refrigerator before piping.