Technically, “pain au lait” can be translated from French as “milk bread”, where “pain” means “bread” and “lait” means “milk”. However, Oxford dictionary gives a bit different translation, namely “milk roll” (“Pain Au Lait” n.pag.). Some sources translate “pain au lait” as “sweet bun” (“At the Boulangerie” n.pag.). The French name implies that “pain au lait” is a type of French bread. Different types of French bread are known to the whole world for their rich taste, crispy crust, various shapes, and baking techniques.
“Pain au lait” is more related to pastry than bread. In fact, it can be referred to as a viennoiserie. Viennoiserie is a group of French pastries that can be made from yeasted sweet and leavened dough or from puff pastry dough which becomes puffy during the process of baking. “Pain au lait” is sweeter than bread, and milk is the only liquid ingredient used to make it. Unlike brioche, “pain au lait” does not have eggs in its recipe, and the amount of butter is reduced in comparison to the recipe for brioche. The reason these two are compared is that both are usually eaten for breakfast or as snacks. “Pain au lait” is made in shape of small rolls, buns or loaves. The dough is folded to make the texture of the final product flaky and soft.
Knowing the history of viennoiserie, one might assume that “pain au lait” and some other pastries are not entirely of French origin. There is an interesting story about the arrival of the Austrian pastry to France. The Turks decided to conquer the Austrian city of Vienna in 1683. However, the siege failed because of the Austrian bakers. As usual, the bakers worked at nighttime and some of them heard loud sounds of digging near their bakeries. When bakers alerted the military commanders of that, the latter found the Turks who tried to dig tunnels under the walls to get access to Vienna. The Turks were defeated soon. To honor the role of bakers in the defeat of Turkish soldiers, the Austrian Emperor ordered to create a sweet yeast roll in the shape of the crescent like the one on the Turkish flag.
In 1770, these crescent shaped rolls were introduced in Paris. French bakers wanted to honor the Austrian Princess Marie Antoinette who had arrived to France to get married to King Louis XVI, so they made the pastries that would be familiar to the Princess. In France, those Austrian pastries became known under the name of “croissant”. Later, the croissant-making technique was improved and popularized.
In 1839, a retired Austrian officer August Zang opened a bakery in Paris and named it Boulangerie Viennoise. He introduced a new technique, namely a steam oven that was used to give patisserie its fluffy and crispy texture. Yeasts used in the Viennoise patisserie allowed getting results that were not achievable with natural cultures. The Viennese bakers enriched bread with eggs, milk and butter to make their products flaky and crispy. Actually, it was different from the traditional bread making techniques of their French counterparts.
Some sources mention that milk dough was introduced in 1928. It was a recipe for petits pains viennois, or small Viennese loaves published in the seventh edition of Gastronomie Pratique by Henri Babinski (Ali-Bab) (“Elizabeth David and the Mystery of Petits Pains au Chocolat” n.pag.). The named recipe included almost the same ingredients as the modern recipes for “pain au lait”. However, it included water in addition to milk. Up to this day, it is not clear whether it was “pain au lait” or its early variation However, its name hints at the possibility of the Austrian origin for this milk bread (“Elizabeth David and the Mystery of Petits Pains au Chocolat” n.pag.). A recipe for petits pains au lait was published in the book La Boulangerie d'Aujourd'hui of Urbain Dubois written in 1933.