Texte d'origine - Anglais - Cook until custard is thick or until it coats the...

Esta frase aparece dentro del siguiente párrafo de una receta de cocina: "Separate eggs. Put egg yolks in a pot, mix with the remaining sugar. Lightly mix with a folk and add fresh. Place under low heat and cook slowly stirring continuously to avoid yolks coagulation. Cook until custard is thick or until it coats the back of spoon, remove from heat."