Laminating Dough for Croissants

Lamination is folding a sheet of butter into dough again and again to make hundreds of thin layers. Pound cold butter into a flat square. Wrap it in a rectangle of yeasted dough. Roll it out into a long strip, fold it in thirds like a letter, and chill 30 minutes. Do that three times. The butter and dough must be at the same firmness, cool and pliable, around 12 to 15°C. If butter breaks into pieces, it's too cold; if it smears out the edges, it's too warm. In the oven, steam from the butter pushes the layers apart.