Tempering Eggs for Custard: Reaching Nappe Stage. The foundation of a crémeux is a properly cooked crème anglaise — an egg custard that must reach exactly 180°F (82°C) without curdling. The tempering process is essential: pouring a third of the hot liquid into the yolks in a slow stream while whisking constantly raises their temperature gradually, preventing the thermal shock that would scramble them. Once the tempered mixture returns to the pan, constant stirring with a spatula — scraping the bottom and corners where heat concentrates — is critical. The custard is ready at nappe stage, when it coats the back of a spoon thickly enough that a line drawn through it with your finger holds its shape cleanly. An instant-read thermometer removes the guesswork: at 180°F the egg proteins have thickened the custard sufficiently, while even a few degrees higher risks curdling. If small curds do appear, immediately remove from heat and strain through a fine-mesh sieve — this catches most scrambled bits, and a brief blitz with a stick blender can rescue a lightly curdled custard. The hot strained custard is then poured directly onto chopped chocolate, creating an emulsion that sets into the characteristic silky crémeux texture after chilling.