Bread, Cinnamon Sourdough Pullman

The loaf I want for French toast: enriched, sourdough, baked in a Pullman pan with the lid on and degassed at shaping. Swirled, not glazed. Egg wash between the layers, flour in the filling, no butter in the swirl. ⚠ I have not baked this. The whole thing is the reasoned answer, not a proven one — every number below is my starting point, and I’d expect to move some of them.

Ingredients

• ⚠ UNTESTED. These quantities are a reasoned starting point, not a sourced formula.
• The dough — moderately enriched
• 500 g bread flour
• 100 g stiff, active levain — a larger inoculation than usual, because fat and sugar slow the starter down
• 250 g whole milk — hydration on the low side of instinct; the egg and butter bring liquid too
• 1 large egg (about 50 g)
• 50 g sugar — keep it modest; see the notes on why a very sweet dough browns badly
• 60 g softened butter
• 10 g salt
• The filling — every element of this is a King Arthur test result
• 60 g sugar
• 2 Tbsp ground cinnamon
• 2 Tbsp flour — this is not optional. It absorbs the syrup.
• The binder — this is the big one
• 1 large egg + 1 Tbsp water, for the egg wash between dough and filling
• ⚠ NOT butter. Butter is a barrier and it CAUSES the gap. Do not brush the swirl with butter.
• ⚠ NO GLAZE. Read the notes — the numbers don’t allow it.

Directions

Key ingredients

Cinnamon

1. Build a stiff, active levain and use a larger inoculation than you would for a lean loaf. Fat and sugar slow fermentation; expect a longer bulk than your instinct says.
2. Mix the dough. Ferment warm-ish. Do NOT retard it for three days — that’s the acetic path, and see the notes.
3. Degas thoroughly at shaping. This is the step that makes the crumb, and it is not a compromise — read the notes.

Roll the dough out into a rectangle.

1. Brush a thin layer of egg wash on the dough BEFORE the filling. The egg protein coagulates in the oven and acts as glue, cementing the dough layer to the filling layer. Water or milk work but bind less well. Butter does the opposite — it keeps the layers from cohering. Skip it.
2. Stir the flour into the cinnamon sugar and sprinkle the filling over the wash.
3. Roll tight, and degas as you roll. Trapped air becomes a void. Keep any inclusions small — pulse raisins to ¼ inch or less; big chunks force gaps and fight shaping.
4. Into a buttered 9×4 Pullman pan. Proof. Put the lid ON. The lid suppresses oven spring and prevents a domed, cracked, open top — and the constrained rise gives the swirl less room to separate.
5. Bake around 375°F for about 40 minutes, to an internal 190–200°F. (That bake schedule is standard Pullman practice, not a sourced number for this formula. Adjust.)

Cool completely before slicing.

1. For French toast: slice ¾–1 inch thick and oven-dry the morning you cook — 275°F for 10–15 minutes, no colour. Do not leave it out overnight. See French Toast, The Custard Test.

Notes

⚠ MARK THE WHOLE LOAF UNTESTED

I have not baked this. It’s the reasoned answer assembled from established chemistry and one genuinely tested source, and I’d rather hand you that honestly than dress it up as a proven formula. The quantities are my starting point. The reasoning below is the part worth having.

The reframe: open crumb comes from artisan boule practice, not from the starter

This is the strongest inference in the whole project and it corrected an assumption I didn’t know I had.

French toast is a soaked product. The custard has to be held in suspension inside the slice and set there. A tight, fine, even crumb behaves like a sponge with small uniform cells — capillary action pulls custard in and surface tension holds it against gravity. An open, irregular crumb has large interconnected voids: custard enters and drains straight back out, because the voids are too big for capillarity to hold liquid. You get a slice that’s soggy at the bottom edge and dry in the middle, with pockets of scrambled egg where custard pooled in a hole. That’s the boule failure mode.

But open crumb is a product of high hydration, minimal degassing, gentle handling and steam-baked free-form loaves. It is NOT an inherent property of sourdough. Put a moderately-hydrated dough in a lidded Pullman, degas it at shaping, and you get a fine, even, close crumb regardless of whether the leavening is commercial yeast or a starter. Sourdough’s reputation for open crumb is a reputation of artisan practice, not of the microbiology.

The pan delivers the structure. The sourdough adds flavour at no structural cost.

That’s why this isn’t a fudge. It’s the best of both, and long ferment is a free upgrade — organic acids and depth, the honest reason store-bought cinnamon bread tastes like sweetened cardboard.

And enrichment isn’t opposed to sourdough. Butter, egg, milk and sugar in a sourdough Pullman is entirely conventional — you get the egg-protein network AND the fat AND the tight crumb AND the fermentation flavour. The egg protein is already coagulated in the crumb, so it resists collapse when the slice is saturated and handled wet. The fat slows staling and keeps the crumb from disintegrating. The pan crust is thin and soft, where a rustic crust is a glassy dehydrated shell that doesn’t absorb custard at all and fights the fork.

⚠ Keep the ferment LACTIC, not acetic

Sourdough acidity is lactic (mellow, yogurty) plus acetic (sharp, vinegary), and the ratio is yours to control: warm, wet, fast fermentation favours lactic; cold, stiff, long, oxygen-exposed fermentation favours acetic.

• A mild lactic tang against sweet cinnamon custard is a genuine asset — same logic as buttermilk in pancakes. Acid cuts richness and stops a very sweet, very fatty dish cloying. And you’re putting syrup on top of custard, so some acid is probably actively good.
• A pronounced acetic tang is a liability. Vinegar-sharp plus cinnamon plus maple is a muddle.

Ferment warm-ish. Don’t retard for three days. This is a steerable variable, not a fixed cost of using sourdough.

(No controlled sensory study of sourdough acidity in French toast exists — NOT FOUND. And whether the sourdough flavour even survives being soaked in custard, fried in butter and drowned in syrup is genuinely untested. My guess: it partially does, reading more as “this doesn’t taste like nothing” than as “this tastes like sourdough.”)

⚠ NO GLAZE. Two numbers settle it.

	Temperature
Sucrose begins to caramelize	320°F / 160°C (deep caramel 338–356°F; scorch ~375°F)
Diluted custard sets, interior	176–185°F / 80–85°C

The custard needs its interior at ~180°F, and heat has to conduct through a wet slice to get there — several minutes a side. Meanwhile the surface, once it dries, climbs toward pan temperature, right into the caramelization band.

A bare slice is already at the edge of the sugar-burn window, and the only thing saving it is the custard’s water keeping the surface cool while the inside cooks. A glaze breaks that protection: it’s a concentrated sugar film sitting outside the custard, on the direct-contact surface, with no evaporative cooling of its own. It hits caramelization onset almost immediately and scorches well before the interior sees 180°F.

And this isn’t fixable with lower heat. Turn it down far enough to protect the glaze and the interior never sets — sweet raw eggy bread. The two constraints are genuinely incompatible on a griddle. (An oven-baked casserole is a different thermal regime; that’s why baked French toast recipes have streusel tops and griddle ones don’t.)

Glaze the loaf you eat as bread. Not the loaf you fry. Corollary: keep the sugar in the dough modest too, and let the syrup do the sweetening — a very sweet dough browns fast and unevenly in the pan.

The swirl gap — and this part IS tested

King Arthur ran this and published it, which is more than the rest of this page can say.

The mechanism: sugar is hygroscopic. As the shaped loaf proofs, the cinnamon-sugar filling pulls water out of the surrounding dough and liquefies. That syrup seeps, pools in the bottom of the pan, and leaves a void. The swirl doesn’t “unroll” — the filling literally dissolves itself and runs away, and the gap is where it used to be.

The fixes:

1. Egg wash between dough and filling — the big one. 1 large egg + 1 Tbsp water. The protein coagulates in the oven and glues the layers together.
2. ⚠ DO NOT use butter as the binder. This is the counterintuitive one and it’s why most people’s swirl bread fails: butter acts as a barrier, keeping the rolled layers from cohering. Half the internet tells you to brush the dough with melted butter before the cinnamon sugar. That instruction is actively causing the gap. I’d have buttered it.
3. Put flour in the filling. It absorbs the liquefying syrup and thickens it in place instead of letting it run.
4. Roll tight and degas as you roll.
5. Keep inclusions small.

And the lidded Pullman helps here too — the constrained rise gives the swirl less room to separate.

Spice budget

Cinnamon in the bread — that’s the point of the loaf. But count your sources: if you’re serving it with Syrup, Brown Sugar Cinnamon (Jeff’s) and a cinnamon custard, that’s three cinnamon sources on one plate, and that’s where a real muddle becomes likely. Nutmeg belongs in the custard, fresh-grated. Leave the clove out entirely for the first bakes.

Source: King Arthur Baking, “5 ways to reduce the gap in cinnamon swirl bread” — the one tested thing here.