Laminated Doughs.
Puff pastry has 729 layers of butter after six simple folds. No one counts them; the arithmetic is just multiplication by three.
Laminated doughs are built, not mixed. A lean dough (the détrempe) is wrapped round a flat slab of butter, rolled out long and thin, and folded: a letter (single) fold in three, or a book (double) fold in four. Every fold multiplies the butter layers — by three for a letter fold, four for a book fold — so a croissant's three letter folds give 27 layers and classic puff pastry's six give 729. In the oven, the water in each dough layer and in the butter turns to steam and pushes the layers apart while the butter fries them crisp: hundreds of leaves. Croissant and Danish doughs add yeast, so they rise as well as puff.
The craft is temperature. The butter must be plastic — cool enough not to melt into the dough, warm enough to bend and stretch without cracking — roughly 13–16 °C for most butters, matched to the dough's firmness. Too cold, it shatters into pieces and the layers break; too warm, it smears into the dough and the layers merge. So the dough is rested in the fridge between folds, which also relaxes the gluten so it can be rolled again without shrinking. The workshop folds a dough.
Below: the butter layers after the sequence of letter and book folds you choose (exact multiplication), the thickness of each butter layer when the dough is rolled to the thickness you choose, and the butter's firmness at its working temperature (course melting curve, IX.2).
- Count layers from the folds.
- Keep butter plastic.
- Rest between folds.
- Make croissant and puff pastry.
Multiply by three, keep it cool
Three letter folds give 27 butter layers — a croissant; six give 729 — puff pastry; one letter fold and two book folds give 48. Rolled to 4 mm, a croissant's butter layers are each about 44 µm thick; puff pastry's about 1.6 µm, so thin that further folds start to merge them, which is why puff stops at six. Croissant dough, which must also rise, uses fewer, thicker layers so the yeast's gas has room.
Method for croissants (outline): make a lean, slightly sweet yeast dough, chill it overnight; pound 250 g cold butter into a 15 cm square between paper; enclose it in the dough rolled to a 30 cm square; roll to a long rectangle, letter-fold, wrap and chill 30 minutes; repeat twice more; roll to 4 mm, cut long triangles, roll up from the base, proof at 24–26 °C (warmer melts the butter) until wobbly and doubled, egg-wash, bake at 200 °C for about 18 minutes. Work in a cool room, flour lightly, brush off excess flour before folding, and if the butter feels soft or the dough springs back, chill it.
Make a small rough puff: grate frozen butter into flour, add ice water to bind, and give the dough four letter folds with 20-minute rests. Bake strips and count the layers you can see.
Terms
- Lamination
- Building alternating layers of dough and butter by rolling and folding.
- Letter fold
- Folding dough in three: triples the layers.
- Book fold
- Folding dough in four: quadruples the layers.
- Plastic butter
- Butter cool but bendable, about 13–16 °C.
Sources
- A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.
- H. McGee, On Food and Cooking: The Science and Lore of the Kitchen, 2nd ed., Scribner, 2004.