Always Add Hot Ingredients to Cold

Careful heating is also important during preparation of the mix. Most custard and cream mixes are made by scalding milk or cream—quickly heating it just to the boil— and then stirring it into the combined eggs and sugar. This technique heats the eggs gently but quickly to 140 or 150°F, just 30 to 40°F short of the setting temperature. Doing the reverse—adding cold eggs to the hot milk—would immediately heat the first dribbles of egg close to the boil and cause premature coagulation and curdling.