Name: Purple Sweet Potato Buns
Prep time: 40 min
Cook time: 20 min
Total time: 3 h
Cuisine: Japanese
Ingredients: 175g bread flour (I used Japan High Gluten Flour); 115g full cream milk (whole milk) or fresh milk or water; 1/4 tsp instant yeast; 1/4 tsp sugar; 175g bread flour (I used Japan High Gluten Flour); 200g mashed japanese purple sweet potato (2 potatoes about 250g); All the old dough (above); 2 tbsp (24g) brown sugar; 1/2 tsp instant yeast; 1 tsp salt; 45g egg, whisked; 10 - 20g milk (reserve 10g first and add in later if needed); 50g butter, room temperature; 1 egg + 1 tbsp water, whisked; 8 inches square pan, lined with parchment paper. You can also bake this into a loaf in 450g loaf pan.

Last Updated 2 December 2025

By Bake with Paws

My Purple Bread Journey

I still remember the first time I baked these purple sweet potato buns years ago. I had just discovered the striking hue of Japanese purple sweet potato and wanted to transform it into soft, springy buns that were as beautiful as they were delicious. Over time, these buns have become one of my personal favourite go-to recipes — for their colour, softness, and the warm, homey feeling they bring to the kitchen.

Every time I slice into a freshly baked batch, the gentle violet crumb and subtle earthy-sweet aroma remind me of why I fell in love with bread making in the first place.

Why I Love These Buns

Naturally vibrant colour — no dyes needed: The purple sweet potato gives the buns a beautiful violet hue, making them visually striking and perfect for breakfast, gifting, or a tea table centerpiece.
Soft, tender crumb with subtle sweetness: Thanks to the moisture and natural sugars in the sweet potato, the crumb remains soft, slightly sweet, and inviting.
Fine, springy texture with old dough: I use the Old Dough method (pâte fermentée) rather than Yudane. From my experiments, this method produces a finer, softer texture than straight dough. The slow fermentation enhances aroma, flavour, and structure, giving the buns a professional, bakery-style finish.
No need for Yudane method: Although Yudane can make some breads extra soft, it’s not ideal here because potato starch absorbs more water than wheat starch. Using Yudane would make the dough too moist, potentially gummy, and unnecessary for these buns. Old dough works better for a balanced, soft, and flavorful result.
Moisture retention and shelf life: The combination of potato starch and pre-fermented dough keeps the buns soft longer without compromising texture.
Comforting and wholesome: These buns aren’t just pretty — they bring a warm, homey feeling to the kitchen with every bite, making them one of my all-time favourite recipes.

How To Make Purple Sweet Potato Buns

Ingredients (Yields: 9 Buns)

Old Dough:

175g bread flour (I used Japan High Gluten Flour)

115g full cream milk (whole milk) or fresh milk or water

1/4 tsp instant yeast

1/4 tsp sugar

Main Dough:

175g bread flour (I used Japan High Gluten Flour)

200g mashed japanese purple sweet potato (2 potatoes about 250g)

All the old dough (above)

2 tbsp (24g) brown sugar

1/2 tsp instant yeast

1 tsp salt

45g egg, whisked

10 - 20g milk (reserve 10g first and add in later if needed)

50g butter, room temperature

Egg Wash:

1 egg + 1 tbsp water

Utensil:

8 inches square pan, lined with parchment paper. You can also bake this into a loaf in 450g loaf pan.

Step-By-Step Method:

Old Dough

Combine water/milk, yeast and sugar in a mixing bowl. Then add in bread flour and mix with hand until become a soft dough. Roll into a ball and place in a greased bowl. Cover with cling film and let it proof 1 hour in room temperature (28C).
After 1 hour, place into the refrigerator overnight for at least 12 hours or up to 16 hours. Fridge temperature 2C - 4C. The next morning, take out the old dough from refrigerator to return to room temperature 30 minutes before using. You can also use directly from the fridge if you forget to take out earlier.
If you don't plan to bake the next day, after 1 hour fermentation, shape it into a ball and wrap it in cling wrap or place it in a ziplock bag. Store it in the freezer for 1-2 months. Take it out 30 minutes before using to defrost.

Mashed Purple Sweet Potato:

Wash, peel and cut the potato.
Steam for 15 minutes or until potatoes are soft.
Mash the potato with a potato ricer or masher. Set aside to cool.

Kneading Main Dough:

Put all ingredients (except butter) including all the old dough into a bowl of stand mixer. Using the paddle attachment, mix for 2 minutes or until all incorporated. Please add 1 tablespoon of milk/water if the dough is slightly hard and dry. Change to hook attachment and knead for another 3 minutes or until the dough comes together. Add in butter and continue knead for 10 - 12 minutes or until reach window pane stage. During the whole kneading process, I stopped few times to scrape down the dough from the hook to be sure it is evenly kneaded and also to prevent the motor from overheating.

1st Proofing:

Let the dough rise in a warm place for 45 to 60 minutes or until double in size in a large greased bowl, covered with cling film or kitchen towel.

To shape:

Punch down the dough to release the air. Transfer the dough to a clean floured surface then divide into 9 equal portions.
Form each portion to a ball. Please watch the video "How to shape the Buns"
Place all dough balls in a prepared baking pan.
Let the dough rise for 30 - 45 minutes or till about 90% of the size.

To bake:

Preheat the oven at 190C (top and bottom heat) or 170 (fan-forced mode) for 10 minutes.
Brush with egg wash.
Bake at preheated oven for about 15 - 20 minutes, or until golden brown.
Remove buns from oven and the pan, let the buns cool on rack.

Expert Tips for Success

Use the right flour: Use a strong bread flour (ideally high-gluten flour) for optimal gluten structure. It helps the dough hold its shape and gives a soft but resilient crumb.
Steam the sweet potatoes, don’t boil: Steaming helps preserve the natural purple colour and nutrients better than boiling. (Boiling may dilute colour and water-log the potatoes.)
Reserve some liquid: Always reserve part of the milk/water for final hydration — each flour and potato batch absorbs liquid differently. Add the reserved liquid gradually to avoid overly sticky dough.
Watch your dough temperature: In warm climates (like Malaysia), warm dough can become sticky or over-proof quickly — using cold milk or chilling your bowl/attachments can help.
Use pre-fermented dough (old dough / pâte fermentée): This improves flavour, crumb softness, and shelf-life compared with straight dough. I always make the old dough fresh the night before if I don’t have a saved portion.

Common Mistakes to Avoid

Baking purple sweet potato buns can be tricky if you’re not careful. Here are some common mistakes and how to avoid them:
Using too little liquid or a stiff dough: Since sweet potato starch absorbs a lot of water, insufficient liquid can make the dough dry and the buns dense. Always add reserved liquid gradually and adjust as needed.
Adding too much liquid: On the other hand, too much liquid can make the dough sticky and hard to handle. Keep an eye on hydration, especially if your sweet potatoes are very moist.
Over‑ or under‑kneading the dough: Under‑kneading results in poor gluten development and dense buns, while over‑kneading — especially in warm conditions — can weaken the dough. Knead until the dough is smooth and elastic.
Over‑proofing during the second rise: Letting the buns rise too long can cause them to collapse or shrink in the oven. Aim for about 90% of the desired rise before baking.
Using the Yudane method for this bread: While Yudane works well for some breads, it’s not suitable here. The potato starch absorbs too much water, making the buns overly moist and gummy. The Old Dough (pâte fermentée) method gives a much better texture and flavor.

Serving Suggestions & Storage

Serving: These buns are lovely warm and soft — enjoy on their own, or slice and spread with a bit of butter, cream cheese, or even a swirl of jam. Their natural purple colour makes them a lovely addition to breakfast, tea time, or a picnic.
Storage: Store cooled buns in an airtight container at room temperature for 2–3 days. For longer storage, freeze in a resealable bag — when needed, thaw at room temperature or reheat gently in a microwave or steamer for a minute or two to revive softness. Much like other potato-based breads and buns, the moisture helps maintain softness after freezing. (This storage principle is similar to how I store my other enriched breads.)
Reheat tip: Lightly mist buns with water before reheating to help restore moisture and softness.

FAQ

Q: Can I replace old dough with straight dough?

A: Yes — when I initially developed this recipe I used straight dough. It works — but buns are noticeably softer, with better crumb and shelf-life when using old dough (pâte fermentée).

Q: Is it okay to use orange or white sweet potatoes?

A: You can — but expect differences in colour (no purple hue), flavour (sweeter for orange), and crumb moisture. The unique violet crumb comes only from purple sweet potato.

Q: Can I make these buns without butter (vegan / lighter version)?

A: You may substitute butter with oil or omit — but the final bun will be less rich and slightly less tender. Using plant-based milk and oil gives a decent dairy-free version.

Q: My buns turned out gummy — what went wrong?

A: Likely too much liquid due to potato starch absorbing more water, or over-proofed dough. Next time, adjust hydration carefully and avoid over-proofing.

Q: Why did the purple colour fade after baking?
A: Natural pigments in purple sweet potatoes (anthocyanins) can degrade with overcooking or too much moisture. Steaming potatoes instead of boiling, and avoiding over-baking helps preserve the violet hue.

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Have a Question or Tried This Recipe?

I’d love to hear from you! If you have any questions, or if you bake these buns and want to share your photos/feedback — drop a comment below. Tag your creations on Instagram with @bakewithpaws. Your feedback helps me improve and create even more recipes you’ll love.

Related Recipes You’ll Love

Purple Sweet Potato Soft Sourdough Buns — for a naturally leavened, rustic version.
Purple Sweet Potato Loaf — soft, vibrant loaf bread for toast or sandwiches.
Orange Sweet Potato Bread — Soft and fluffy.

Comments

Yunie20919 August 2019 at 08:06
This is super awesome! Ive baked it and gonna bake more and more. Tq for the great recipe!
John Smith30 September 2019 at 14:38
Rats! Mine had a bitter taste..do you know why it might have turned out like this for me?
John Smith30 September 2019 at 14:39
Rats! My buns turned out bitter for some reason. Do you know what I might have done wrong? Or did I just have bad sweet potatoes?
KC27 December 2020 at 03:31
May I know if I could omit the sweet potato for the plain bun version? Thanks !
Janice26 July 2021 at 00:35
Hi YL, for this recipe, Purple Sweet Potato Buns (Old Dough Method) using 450g covered loaf pan, what is the temperature and how long to bake?
Anonymous29 May 2022 at 01:57
Hi, may I substitute instant yeast with active yeast ?

BAKE WITH PAWS

Purple Sweet Potato Buns — Soft & Naturally Violet