Amy Scherber’s Sponge Starter – Tvfn

Mix all the ingredients together in a medium bowl and stir vigorously
with a wooden spoon for 2 to 3 minutes, until a smooth, somewhat
elastic batter has formed. The batter will be very stiff; it gets
softer and more elastic after it has proofed. You may find it easier
to mix the sponge using electric mixer, with a paddle or a dough
hook, on medium speed for 1 to 2 minutes. Scrape the sponge into a
2-quart clear plastic container and cover with plastic wrap. At this
point you have two options:

If you plan to make your dough later that same day, let the sponge
rest at room temperature until it has risen to the point where it
just begins to collapse. This may take from 6 to 8 hours, depending
on the temperature of the sponge, the temperature of the room, and
the strength of the yeast. The sponge will triple in volume and small
dents and folds will begin to appear in the top as it reaches its
peak and then begins to deflate. The sponge is now in perfect
condition to be used in a dough. It’s best if you have already
weighed or measured out all of your other recipe ingredients before
the sponge reaches this point so you can use it before it collapses
too much.

If you’re not planning to make your dough until the next day or the
day after, put the covered sponge in the refrigerator and let it rise
there for at least 14 hours before taking it out to use in a recipe.
Be sure to compensate for the cold temperature of the starter by
using warm water (85 to 90 degrees) in the dough instead of the cool
water specified in the recipe. Or let the starter sit out, covered,
until it reaches room temperature (this may take several hours)-but
don’t let it collapse to much before you use it.