To add more flavor to breads, many bakers use pre-ferments, in which a portion of the bread flour is mixed with water, occasionally salt, and a tiny bit of yeast, and is then allowed to ferment for a long time – 12-18 hours, usually. There are three basic types of pre-ferments, and they usually account for anywhere from 15% to 40% of the dough:
Poolish: Most famously used to make tasty baguettes, a poolish consists of equal weights of flour and water (or 2 parts flour to 1 part water by volume) with just a tiny bit of yeast. For home bakers, a pinch or 1/16 of a tsp should be more than enough.
A poolish is ready when it is very bubbly, smells sweet and has just begun to recede from hits high point.
Biga: Truth be told, “biga” is just an Italian word for pre-ferment, but in the English speaking world, it has come to mean a stiff preferment, usually a dough at about 60% hydration with just a pinch of yeast. It should be kneaded for a few minutes after it is mixed up.
A biga is ready when it has begun to recede just slightly in the center.
Pate Fermente: Literally, this is French for “old dough,” and it’s just what it sounds like. In France, they’ll often save dough from the previous day’s batch, keep it in the fridge, and then used it in the next day’s batch. Typically, though, home bakers make one by exactly mimicking the proportions of flour, water and salt, and adding just a tiny pinch of yeast. It is then allowed to ferment for a long period of time.
Alternatively, once could even use the same proportions of yeast, but only let it ferment for an hour or so on the counter, and then placing it in the refrigerator.
Like a biga, a pate fermente is ready when it just begins to recede in the center.