What is a Danish pastry?

The origin of the Danish can be blamed on a strike amongst the bakery workers in Danish bakeries in 1850. The strike forced bakery owners to hire foreign workers, including Austrian bakers. Unfamiliar with the Danish baking recipes, they baked pastries from their native recipes. Amongst these Austrian pastries were Plundergebäck, which became quite popular in Denmark. Later this recipe was changed by Danish bakers, increasing the amount of fat (by adding more egg) which resulted in what is today known as the Danish.
The ingredients for the Danish pastry include flour, yeast, milk, eggs, and generous amounts of butter. A yeast dough is rolled out thinly, coated with butter, and then folded into numerous layers. The rolling, buttering, folding, and chilling are repeated several times to create dough which is fluffy, buttery and flaky.
The presence of both yeast in the recipe as well as steam make the Danish rise. The layers of butter help separate the dough into the tender flakiness that distinguishes good Danishes. When baked, the butter worked into the layers of dough gives off moisture, and the resulting steam causes the thin layers of dough to puff and rise.
The Danish as consumed in Denmark can be topped with chocolate, sugar or icing, and may be stuffed with either jam, marzipan or custard. There are a range of shapes including circles with filling in the middle (known as "Spandauer's"), figure-eights or spirals (known as snails).