okinawan sweet potato scones

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At first glance, Okinawan sweet potatoes look pretty ordinary. The skin of this starchy root vegetable is thin, dull, and beige. However, slice one open and you’ll find that the insides are a marvelous violet! When cooked, the color intensifies and ranges from mauve to dark purple. Similar to their orange counterpart, Okinawan sweet potatoes are delicious and versatile. Roasting yields a creamy texture and a slightly sweet, earthy, and nutty flavor. Like blueberries and eggplants, Okinawan sweet potatoes contain anthocyanin, the pigment that gives these foods their natural purple color. Anthocyanins are powerful antioxidants with numerous health benefits. Sources indicate that Okinawan sweet potatoes have 150 percent more antioxidants than blueberries!
The high concentration of anthocynanins consequently created an interesting baking challenge. My attempt to make Okinawan sweet potato scones inadvertently turned our kitchen into a mini laboratory.  For my first batch of scones, I opened the oven door to find that my gorgeous purple dough had turned greenish blue! Had I paid more attention in chemistry class I might have remembered that anthocyanins are pH dependent. When exposed to different levels of acidity or basicity, anthocyanins change color. Thus, the absence of an acid and a high pH (too much baking powder & baking soda) in my scone batter produced a green baked good. After a few failed attempts, I finally got the recipe right. I increased the acidity via homemade coconut buttermilk (coconut milk + white vinegar) to lower the recipe’s pH. The final result? A mouthwatering scone laced with glorious chunks of dark purple sweet potato. To finish, I topped each scone with a drizzle of lavender colored icing, made from blended sweet potato, coconut milk, and powdered sugar.

The how to…
Recipe adapted from Cook’s Illustrated
15 2 1/2 inch round scones

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1 cup mashed sweet potato, about 3 small Okinawan sweet potatoes
1 egg, beaten
2 1/4 cups all-purpose flour
2 tsp baking powder
1/2 tsp baking soda
1/2 tsp salt
1/3 cup granulated sugar
6 Tbsp frozen unsalted butter, diced
light coconut milk, for milk wash

Coconut buttermilk
1 cup light coconut milk
1 Tbsp distilled white vinegar

Okinawan sweet potato glaze
1/2 cup powdered sugar
1 Tbsp roasted Okinanwan sweet potato
1 Tbsp light coconut milk

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  1. Make sweet potato mash. Preheat oven to 400 degrees. Wipe potatoes with a damp cloth and prick with a fork. Place directly on oven rack and roast until soft, about 50-60 minutes. Carefully remove from oven and let cool completely. Scoop out the insides and mash (1 cup is needed for recipe). Set aside.
  2. Prepare coconut buttermilk. In a small cup, combine coconut milk and vinegar. Let sit for 10 minutes.
  3. Wet ingredients. In a medium bowl combine coconut buttermilk, sweet potato mash, & egg. Whisk until well incorporated. Set aside.
  4. Dry ingredients. In a separate bowl, combine flour, baking powder, baking soda, salt, & sugar and mix well. Add diced butter and cut into flour with a pastry blender or fork until mixture is crumbly and butter resembles small pebbles.
  5. Combine. Add wet mixture to flour mixture and fold until just combined. Turn dough out onto a floured counter and dust surface of dough with flour. Using floured hands, knead dough 6-8 times (add flour as necessary to prevent sticking) until dough comes together into a ball. Dust dough with additional flour and roll out with a rolling pin. Stamp out rounds using a biscuit cutter and place on a sheet pan lined with parchment paper. Lightly brush the tops with coconut milk and bake in a preheated 425 degree oven until golden brown, about 25 minutes. Remove from oven and let cool completely.
  6. Glaze. Combine glaze ingredients in a blender (I used a Bella Rocket Blender) and process until smooth. Drizzle glaze over scones and serve.

Some extras…
*Sweet potato mash can be made up to 2 days in advance. Store in refrigerator until ready to use.
*Any tinge of green that might appear in the batter (due to the chemical reaction noted above) should disappear once the baked scones are allowed to fully cool.
*In NYC, Okinawan sweet potatoes are available in Asian markets in Chinatown.

10 responses to “okinawan sweet potato scones

  1. Hi Kara, this is the coolest thing ever! ! ! I feel like maybe this is one of the most inventive and enticing baking recipes I’ve seen in the blog world!

    Thank you for the last asterisk! I was wondering where I could get my hands on some!

    Thanks for the chemistry lesson too. I think I missed that class in high school. Lol but I’ve been slowly relearning in the kitchen, just didn’t have the pH languish to describe it! So cool!

    The icing, the coconut buttermilk! Love!


    • Hey!! So glad you enjoyed this post!! Okinawan sweet potatoes are really popular in Hawaii and I’m so glad I found them here. Hong Kong Supermarket in Chinatown is my go to place! The next time I’m down there, I’ll be sure to get you some. Baked goods aside, they are wonderful on its own. And basically, anything made with the orange type, can be made with the purple type (fries, pies, sweet potato mash etc!). Just be mindful of the Ph thing if using leaveners!


  2. I love this post and the discoveries you shared with us–it felt very Cooks illustrated or Harold McGee-esque. The purple colour came out beautifully, especially in that icing!!


  3. Wow, amazing! I’ve been cooking foods from around the world recently and made Mbatata – sweet potato cookies from Malawi! They were really good cookies, but now I’m itching to try your recipe!

    Liked by 1 person

  4. I followed your recipe and my results were a little disappointing. The dough was too wet to knead, even after dusting and the scones still turned green after baking, and the texture is more cake-like. I used regular coconut milk instead of light because that’s what I had. Could that be the reason? That said, it’s very good. Will try again with the remaining mashed ube.


    • Hi Joan! Thanks for your feedback. Sorry to hear that you were disappointed with the recipe, but glad to hear that you liked the taste. It’s possible that regular coconut milk affected the texture, however not the color of the scones. In regards to your batch turning green, again it’s somewhat of a mystery as my final batch turned out perfectly fine! I wonder if using Ube vs. Okinawan sweet potatoes (which is what I used) makes a difference? In any case, use purple potatoes in baking recipes that don’t call for baking soda/powder (e.g. yeast breads etc) and you will have perfectly purple baked goods!!! If you try the recipe again, or make any changes, I’d love to hear about it. Happy baking!


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