Begin with making the crémeux. Place the chocolate in a heatproof bowl set over a saucepan of gently simmering water (don’t let the bowl touch the water). Stir occasionally until melted and smooth. Cool slightly.
Place the egg in a heatproof bowl. Place the milk and cream in a saucepan over medium heat. Bring just to a boil. Whisking continuously, add the hot c