Poppyseed crusted Tangzhong Purple Sweet Potato Sandwich Loaf

Poppyseed crusted Tangzhong Purple Sweet Potato Sandwich Loaf

I’ve posted a previous purple sweet potato sandwich loaf which was enriched with brown sugar and butter. I wanted to try making a loaf with the sweet potato but without the animal fat enrichment of the butter and using honey instead of brown sugar. So based on the formula that Maurizio posted on theperfectloaf.com I added mashed purple sweet potatoes to his formula and made adjustments to incorporate the sweet potato.

Total Dough Weight900 grams + sweet potato
Pre-fermented Flour11.00%
Levain in final dough25.96%
Yield1 x 900g Pullman loaf

For 9x4x4 Pullman Loaf Pan

Total Formula

Desired dough temperature: 77°F (25°C). See my post on the importance of dough temperature for more information on dough temperatures.

The rows marked pre-cooked below are the two ingredients cooked (in a water roux, or tangzhong) ahead of time, but they are still counted toward the formula’s overall percentages. In other words, the 8% whole wheat flour is still counted toward the total flour in the formula and is not an “extra” addition.

WeightIngredientBaker’s Percentage
37gPre-cooked (tangzhong): Whole wheat flour (Giusto’s Whole Wheat Flour)8.00%
148gPre-cooked (tangzhong): Whole milk32.00%
347gMedium-protein bread flour or All-purpose flour (~11% protein, Central Milling Artisan Baker’s Craft or King Arthur Baking All-Purpose)75.00%
79gWhole wheat flour (Giusto’s Whole Wheat)17.00%
33gOlive oil7.00%
5gSourdough starter1.10%

Total Yield: 194.90%, 900g

Sourdough Sandwich Bread With Pre-Cooked Flour Method

  1. Prepare Levain – Night before mixing, 9:00 p.m. (Day one)

Mix the following ingredients in a container and leave covered to ripen at about 78°F (25°C) for 12 hours overnight.

WeightIngredientBaker’s Percentage
25gMedium protein bread flour or all-purpose flour100.00%
25gWhole wheat flour 
10gRipe sourdough starter10.00%

Prepare Purple Sweet Potato

You can prepare your purple sweet potato several ways, but you want to have in the end a soft mashed sweet potato. Steaming works well and leaves you with a moist mash. You can also microwave pricking the sweet potato and placing it in a microwaveable dish but something this can be dry. You can also roast the sweet potato, pricking it rubbing it with olive oil and then wrapping it in foil and then baking it until soft.

  1. Pre-cook Flour (Tangzhong) – 8:00 a.m. (Day two)

Be sure to do this ahead of time to give the pre-cooked flour time to cool before mixing.

Milk alternative: If you want to avoid using milk in this recipe, substitute out the dairy milk in the roux, below, for water (or something like oat milk).

37gWhole wheat flour
148gWhole milk

To a medium saucepan, add the flour and milk listed above. Turn the heat to medium-low and cook, whisking continuously, until the mixture thickens and becomes like a paste, about 5-8 minutes. In the beginning, whisk vigorously to break up any flour clumps, and be diligent about this near the end to avoid burning. The mixture won’t seem to do anything until it reaches a critical heat point, be patient; it will thicken.

Once it transforms into a viscous paste (something like oatmeal porridge), remove the pan from the heat and spread it out on a small plate to expedite cooling. Set the tangzhong aside until called for when mixing.

  1. Mix – 9:00 a.m.

I used my KitchenAid stand mixer to mix this dough, but it’s possible to make this bread without a stand mixer by mixing everything together by hand in a mixing bowl. To do this, you’ll need to mix for around 10-15 minutes, depending on your technique (slap and fold will work really well!).

AllPre-cooked flour (see Pre-cook Flour, above)
320gMedium protein bread flour
54gWhole wheat flour
33gOlive oil
107gLevain (see Prepare Levain, above)

To the bowl of a stand mixer fitted with the dough hook attachment, add the pre-cooked flour, flour, water, ripe levain, honey, olive oil, and salt. Mix on low speed for approximately 2 minutes until the ingredients come together, and no dry bits remain. Increase the mixer speed to medium (2 on a KitchenAid) and mix for 8-10 minutes until the dough starts to clump up around the dough hook. It won’t completely remove from the bottom of the bowl, and it will still be shaggy.

Transfer your dough to a bulk fermentation container and cover.

  1. Bulk Fermentation – 9:15 a.m. to 12:45 p.m.

At room temperature, around 72-74°F (22-23°C), bulk should take about 3 1/2 hours.

After 30 mins of bulk do a lamination spreading the purple sweet potato over the laminated dough in thirds. Next slap and fold to combine.

Give this dough two sets of coil folds during bulk fermentation at 30-minute intervals.

After the second set of coil folds, let the dough rest for the remainder of bulk fermentation aim for almost double volume.

  1. Shape – 1:15 p.m.

Prepare a sling of parchment that you can lay your shaped dough onto and then lift to place in the pan. I usually also prepare a length of parchment that goes lengthwise to prevent sticking on the ends of the bread.

I shaped this dough in my typical method for shaping a pan loaf. Check out my guide to shaping pan loaves for detailed instruction.

Once the dough is shaped into a long tube, transfer each to their pan, seam-side-down.

Using either a brush or a spray bottle dampen the top of the dough. At this point, you can sprinkle on any toppings you’d like.

  1. Proof – 1:30 p.m. to 3:30 p.m. (2 hours room temperature)

Cover the pan with a large, reusable plastic bag and seal shut. Let the dough proof at room temperature, around 72-74°F (22-23°C), for 2 hours.

Overnight proof option: before the 2 hour counter proof, cover the pans with bags and place them in your home refrigerator to proof overnight. Bake them the next morning as indicated below. Expect a slightly more sour flavor.

  1. Bake – 3:30 p.m. (pre-heat oven at 3:00 p.m.)


Check on your dough: it should have risen just below the top of the Pullman pan and be very light and airy to the touch (see above). If it’s not quite there, give it another 15 minutes and check again.

I steamed the oven for this bake as described on my post on baking with steam in a home oven.

Preheat your oven, with rack at the bottom third to 400°F (205°C).

Place a pan with a Silvia towel filled with boiling water into the oven about 30 mins before the bread will be loaded.

Once your oven is preheated, remove your proofed loaf from its bag, score it and then slide it into the oven.

Take care to bake the loaf fully; if they are under-baked, the interior will be gummy.

Bake at 400°F (205°C) for 20 minutes with steam. After this time, vent the oven, remove the steaming pan(s), and close the oven door. Drop temperature to 350ºF and bake for an additional 30-40 minutes until the top is well-colored and the internal temp is around 205°F, watch the crust very closely as it might colour very quickly. Remove the pan and gently knock out the loaves onto a wire rack. Return the loaves to the oven to bake for an additional 5 minutes without their pans to add extra color to the bottom and sides.

Let the loaves cool for 2 hours before slicing to ensure the interior is fully set.

Waiting to let the loaf cool before slicing it and making myself a sandwich with it for dinner and I’m starving to it is taking a lot of willpower not to slice it early.