A thin, dry “skin” forms on the surface of puddings because as the mixture is heated. Can this be avoided?
A thin, dry “skin” forms on the surface of puddings because as the mixture is heated, two things happen: Water evaporates, and proteins and sugar become more concentrated. Together, this results in a dry barrier on the liquid’s surface. You can prevent the skin from forming during cooking by stirring, but what about afterward? The most common method is to press parchment paper onto the surface, which prevents evaporation. But this approach can be messy and fussy, particularly when dealing with individual portions in cups or ramekins.
When developing our recipe for Lemon Posset with Berries (see related content), we came up with a simpler way: We let the mixture sit until a skin had formed, passed it through a fine-mesh strainer, and then portioned the pudding and refrigerated it until serving time. The strainer broke up the clumped proteins and sugar, returning the posset to a smooth consistency throughout. We found that this technique will work equally well on other puddings and custards like our Creamy Chocolate Pudding (see related content). After cooking, simply let the pudding or custard cool until a skin forms, about 20 minutes, and then pour it through a fine-mesh strainer into a large bowl. Portion it, and then refrigerate the portions, uncovered, until cool. Cover the cooled portions with plastic wrap (no need to press it onto the surface of the pudding) until serving time.