Basque Cream (Natillas) Dessert Sauce

From Teresa Barrenechea in The Basque Table, this is a great sauce to dress up plain cakes or custards. This recipe accompanies her Recipe #397727 and I didn’t include it in that recipe because the amount it makes is way more than is needed and it throws off the nutritional values considerably! It is the equivalent to pouring custard, natillas (although more liquid than the firmer Santa Fe style natillas) or creme anglais.