Meanwhile, put the egg yolks, sugar, and 2 tablespoons of cold water in a large bowl. Place the bowl over a pan of gently simmering water. Using an electric mixer, beat the egg yolks and sugar for 5–10 minutes, until you are left with a pale, thick foam that holds a trail when the beaters are lifted up. Remove the bowl from the heat and gently fold into the cooled chocolate mixture using a large metal spoon. Let cool to room temperature.