The time you need to cook the cream after the first boil depends on the quantity of liquid you have at the start. As a general rule, you need to cook the cream for 1 minute per 1 litre of Milk (4 cups / 34 oz). This is too make sure that the egg yolks are fully cooked and safe to eat. For this recipe, we are using 0,5 litre of Milk so we are cooking it for 30 seconds. If adapting the quantities of this recipe, make sure to also adapt the cooking time. Don't worry if the cream seems to be rather liquid after cooking it - it will thicken and set in the fridge when cool.