Liquid and Salt

Most recipes use water, though milk or cream is sometimes called for to add richness and flavor. The liquid must be cold enough to keep the gluten development to a minimum. Later it converts to steam in the oven. Obviously, the more moisture in a puff pastry dough, the more steam will be produced, making it possible to get greater lift. On the other hand, you should add no more liquid than is necessary to form a cohesive dough or too much gluten will be developed during the rolling process.

Salt flavors puff pastry. Many pastry chefs feel it is imperative for tightening and stabilizing the gluten.