Impromptu Starter Bread

One overnight preferment, split two ways — a jar of starter to keep, a loaf to bake today · by weight

1 loaf · 20 min

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Start here — weigh your whole preferment
the total e.g. 309 g / 10.9 oz — yours may differ
For the starter jar
57 g (2 oz) of the preferment, set aside
57 g (2 oz) flour, to feed it
57 g (2 oz) water, to feed it
For today's loaf — the remaining ~250 g preferment, plus:
350 g (12.3 oz) bread flour
240 g (8.5 oz) warm water — hold back 20 g
10 g (2 tsp) salt
4 g (1 tsp) instant yeast — so it bakes today

Weigh the whole thing first. Put the preferment bowl on the scale and note the total. Everything below is a split, so the one number you need is what you're starting with. (My batch: 309 g.)
Pull the starter seed — 57 g (2 oz). Scoop 2 oz into a clean jar. Feed it equal weights flour and water — 2 oz each — stir to a thick batter, lid on loose, leave at room temp. That jar is now your future sourdough.
Feed it daily, ~5–10 days. Each day keep about 2 oz and discard the rest, then feed another 2 oz flour + 2 oz water. It'll look alive by day two (that's the commercial yeast), but the real sour builds as wild bacteria take over through the week. It's ready when it doubles reliably a few hours after feeding and smells pleasantly tangy.
Build today's loaf. To the remaining ~250 g of preferment add the 350 g bread flour, most of the water (hold back 20 g), the salt, and the 1 tsp yeast. Stir to a shaggy, sticky dough with no dry flour. Judge the feel: add the held-back water only if it's stiff — leave it out if it's already tacky and slack.
Rest 15 min, then knead ~8 min. Let it sit so the flour drinks, then knead until smooth and elastic. Wet dough — work it with a bench scraper and slap-and-fold rather than flouring it up. (Or do 4 sets of stretch-and-folds over the first hour instead of kneading.)
Bulk rise 1½–2 hr. Cover and let it rise warm until nearly doubled. It's faster than a from-scratch dough because the preferment already did the long ferment.
Shape & proof 45–60 min. Shape a tight boule or bâtard, set it seam-down on parchment, cover, and proof until puffy and slow to spring back. Leave it a touch under — it still needs oven spring.
Bake 450°F with steam, ~35–40 min. A preheated covered Dutch oven is easiest (the lid traps steam); uncover for the last 10 min to brown. Or bake on a stone with a hot water pan below. Pull it at a deep brown, 205–210°F inside.
Cool fully before cutting. At least 30 min on a rack — the crumb is still setting. Hot-cut bread goes gummy.

Steps — tap one to keep your place

1. Weigh the whole thing first. Put the preferment bowl on the scale and note the total. Everything below is a split, so the one number you need is what you're starting with. (My batch: 309 g.)

2. Pull the starter seed — 57 g (2 oz). Scoop 2 oz into a clean jar. Feed it equal weights flour and water — 2 oz each — stir to a thick batter, lid on loose, leave at room temp. That jar is now your future sourdough.

3. Feed it daily, ~5–10 days. Each day keep about 2 oz and discard the rest, then feed another 2 oz flour + 2 oz water. It'll look alive by day two (that's the commercial yeast), but the real sour builds as wild bacteria take over through the week. It's ready when it doubles reliably a few hours after feeding and smells pleasantly tangy.

4. Build today's loaf. To the remaining ~250 g of preferment add the 350 g bread flour, most of the water (hold back 20 g), the salt, and the 1 tsp yeast. Stir to a shaggy, sticky dough with no dry flour. Judge the feel: add the held-back water only if it's stiff — leave it out if it's already tacky and slack.

5. Rest 15 min, then knead ~8 min. Let it sit so the flour drinks, then knead until smooth and elastic. Wet dough — work it with a bench scraper and slap-and-fold rather than flouring it up. (Or do 4 sets of stretch-and-folds over the first hour instead of kneading.)

6. Bulk rise 1½–2 hr. Cover and let it rise warm until nearly doubled. It's faster than a from-scratch dough because the preferment already did the long ferment.

7. Shape & proof 45–60 min. Shape a tight boule or bâtard, set it seam-down on parchment, cover, and proof until puffy and slow to spring back. Leave it a touch under — it still needs oven spring.

8. Bake 450°F with steam, ~35–40 min. A preheated covered Dutch oven is easiest (the lid traps steam); uncover for the last 10 min to brown. Or bake on a stone with a hot water pan below. Pull it at a deep brown, 205–210°F inside.

9. Cool fully before cutting. At least 30 min on a rack — the crumb is still setting. Hot-cut bread goes gummy.

Low salt — salt at the end and taste as you go; broth, cheese, and canned goods already bring salt.