puff pastry

Puff pastry, also known as pâte feuilletée, is a light, flaky pastry, its base dough (détrempe) composed of wheat flour and water. Butter or other solid fat (beurrage) is then layered into the dough. The dough is repeatedly rolled and folded, rested, re-rolled and folded, encasing solid butter between each resulting layer.

This produces a laminated dough. During baking, gaps form between the layers left by the fat melting; the pastry is leavened by steam from the water content of the fat as it expands, puffing the separate layers. The pastry layers crisp as the heated fat is in contact with its surfaces.