Choux pastry, also known as pâte à choux, is a delicate pastry dough used in many pastries. It is a light, airy, and crispy pastry that is used to make a variety of desserts, including profiteroles, éclairs, churros, and more. The essential ingredients for choux pastry are butter, water, flour, and eggs. Instead of a raising agent, choux pastry employs its high moisture content to create steam, as the water in the dough evaporates when baked, puffing the pastry. The high moisture content is achieved by boiling the water and butter, then adding the flour. The mixture is cooked a few minutes longer, then cooled before adding enough eggs to achieve the desired consistency. Choux pastry has a reputation for being difficult, but it is surprisingly simple to make. It is a multi-purpose "paste" that hovers somewhere between dough and batter, and it is thick enough to hold its shape without spreading out flat like a pancake or needing a vessel to contain it, like a Yorkshire pudding. Choux pastry is not sweet, so it is usually filled with pastry cream or other fillings and topped with something sweet, like powdered sugar or ganache.