It’s really just bread dough, only you don’t bake it. Of course, if you make bread regularly enough you can just make a little extra dough and hold it in reserve for the next batch. Pâte fermentée will keep for 3 days in the fridge and about 3 months in the freezer. A basic formula is:
10 ounces bread flour
3/4 teaspoon salt
1/2 teaspoon instant yeast
6 ounces (or slightly more) water
Combine your dry ingredients in the bowl of a mixer with the paddle attached.
Turn the mixer on low and stir for a few seconds, the add the water and stir for about 30 seconds until all the ingredients are moistened.
Switch to the dough hook and knead for five minutes. You want a firm and slightly tacky dough.
Put the dough into a bowl and cover it with plastic wrap.
Let it ferment at room temperature for an hour, until it’s increased in size noticeably.
The put it into the fridge overnight. The next day — presto chango — you’ll have made pâte fermentée. Use it right away, within 3 days, or freeze.