Purple Sweet Potato Butter Mochi
Purple sweet potato butter mochi combines the classic local Hawaiian mochi dessert with another beloved food in Hawai’i: the purple Okinawan sweet potato. Disclaimer: This post may contain affiliate links. As an Amazon Associate I earn from qualifying purchases.
What is Okinawan Sweet Potato?
You might be familiar with Okinawan sweet potatoes if you’ve watched the Netflix documentary on Blue Zones, called Live to 100. Okinawan sweet potato is a sweet potato from the morning glory family with light brown skin and bright purple flesh. When cooked, the flesh becomes a striking dark violet. As the name implies, this sweet potato is commonly grown in Okinawa, Japan. Studies on this nutrient rich sweet potato have connected it with the famously long life span of Okinawans.
Okinawan sweet potatoes are also very popular in Hawai’i! And you know what else is popular in Hawai’i? Butter mochi. So of COURSE I had to put the two together!
Purple Sweet Potato Substitutions?
In the mainland US, you may be able to find Okinawan sweet potatoes in Asian markets. In my experience, they are not always available and/or can be extremely expensive. But if you can find it, it’s totally worth it!
If you don’t have access to Okinawan sweet potatoes, you may be able to find Molokai sweet potatoes as a substitute. They are sometimes sold as “purple yams,” and have dark purple skin and flesh. A strain of Hawaiian purple sweet potatoes have also been patented by a farm in North Carolina and sell them as “Stokes” sweet potatoes, if you can find those.
If you can’t find any of these varieties, you may have better luck using my ube butter mochi recipe, which has a similar flavor and color, but uses ube jam, which is more widely available.
How to Cook Okinawan Sweet Potato
You can cook Okinawan sweet potatoes the same way you cook other sweet potatoes or yams. To use the flesh in dessert recipes like this one, I like to microwave my potatoes until soft, peel the skin, and mash the insides. However, you could also bake them in the oven.
Butter Mochi FAQs
I have so many butter mochi recipes on this blog and on my social media! Here are some of the frequently asked questions about my butter mochi recipes and tips for butter mochi making.
Is butter mochi gluten free?
Yes! Typical butter mochi consists of only mochiko, which is a rice flour. This recipe also uses Okinawan sweet potato, so there’s still no gluten.
What does butter mochi taste like?
Butter mochi is essentially a cake. The mochiko flour makes the texture denser and bouncier than a typical American cake. Some people seem to expect butter mochi to be chewy and stretchy, but that texture is really only found when you have pure mochi made from rice only. Butter mochi really just tastes like a denser cake. With the addition of sweet potato in this recipe, there is more of a bite and slightly less fluffiness, but otherwise it is very similar to other butter mochi recipes.
Can you freeze butter mochi?
Normally, yes. However, I’ve found the Okinawan sweet potato doesn’t freeze and rethaw very well, resulting in a harder butter mochi after it’s been frozen, so I don’t recommend freezing this particular recipe.
More Okinawan Sweet Potato Recipes
Looking for more ways to cook with Okinawan sweet potatoes? Check out these recipes:
- Okinawan Sweet Potato and Haupia Pie Bars
- Okinawan Sweet Potato Haupia Pie
- Purple Sweet Potato Latte
Purple Sweet Potato Butter Mochi
Ingredients
- 8 oz mochiko, about 1 3/4 cups or half a box
- 3/4 cup sugar
- 1 tsp baking powder
- 1/2 tsp salt
- 12 oz mashed Okinawan sweet potato, about 2 cups, from 2 medium-large Okinawan sweet potatoes
- 1 14 oz can coconut milk
- 4 oz butter melted, 1 stick
- 1 tsp vanilla extract, can sub other extracts
- 2 eggs
Instructions
- Preheat oven to 350 degrees F and grease an 8×8" baking dish.
- Mix all ingredients in a large mixing bowl, stirring well to ensure no dry lumps of flour remain.
- Pour into your prepared baking dish and bake for 45 minutes or until a toothpick inserted in the center comes out clean.
- Allow butter mochi to cool before slicing and serving. This butter mochi is best eaten fresh, as it dries out more quickly than some of my other recipes. However, leftover butter mochi can be kept in an airtight container in the fridge or frozen; just let it come back to room temperature before eating.
Notes
- You can double this recipe and bake it in a 9×13″ baking dish for one hour.
- I highly recommend using a digital kitchen scale to measure your mochiko. Differences in the amount of mochiko may result in differences in the thickness of your batter, which will affect bake time.
- To prep your Okinawan sweet potato, you can poke holes in it with a fork and microwave for 5-6 minutes until it can be easily pierced. Peel the skin and mash the purple flesh for this recipe. If you don’t want to use the microwave, you can also cook these sweet potatoes in the oven, just as with other types of potatoes. However, this will add at least an hour to your preparation time.
This was a a great sweet potato recipe! I like how it uses less eggs. I decreased to 6 tablespoons of butter, 3/4 of a stick instead of a whole stick, and also a little less than 2/3 cup sugar instead of 3/4, and it was perfect for my taste buds! the sweet potato was very sweet so that really helped decrease the amount of sugar I needed to add. Thank you for your recipes! I like how they are so easy to adjust. According to the ingredients you have on hand and your personal preference.
This was amazing!
Woohoo! Thanks for taking the time to review!
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I’ll definitely try this today. I find that steaming the sweet potatoes a much better alternative, just peel sliced and 1/2 inch pieces and steam for 5 minutes. So simple. I did this with some broccoli and cauliflower for dinner 😇🙏💕
I agree, steaming definitely has great results! Microwave is great for convenience and those who don’t have a full kitchen.
I love this recipe. I add 50% more purple sweet potato to make this a tad bit healthier, but the recipe is great as is too!
Thanks, Janice! Adding more sweet potato sounds yummy!
I think I added too much mochiko because it was a pretty thick batter, and turned out not as gooey as I typically like my mochi, BUUUTTTT, it still turned out great, and I need someone to share this with before I eat the whole pan. Mahalos!
Aloha and thanks for the recipe! If I’m doubling the recipe to fit a 9×13 pan, how long is the bake time? I’m thinking about 60-70 minutes at 350°F- any guidelines? Also, I say one of the best ways to cook Okinawan sweet potatoes is to cut them into large chunks (2-inch+ thick pieces), unskinned, and then use an Instant Pot. Place cut pieces on a trivet, add a cup or so of water, and cook at high pressure for 25-30 minutes. When done, quick-release, remove the trivet, place the sweet potatoes on a cutting board, and using a fork or spoon, slip the skins off while still hot. The sweet potatoes come out a deep purple and soft…
Hi Randy, thanks for the tip about the Instant Pot! For 9×13 bake time, sometimes mine has been done as early as 45 minutes but I would not be surprised if it did take up to an hour.
I just made this last night and it was so delicious!! It was one of those desserts that I shared with friends and family but afterwords wished I had just kept it all for myself haha. I used stokes purple sweet potatoes and the color was super vibrant. I didn’t have quite enough coconut milk so I substituted a mix of cream and almond milk for the last few ounces of liquid and the mochi still came out perfectly. I baked mine an extra 10 or 15 minutes because I love my butter mochi with browned edges!
Woohoo! Thanks so much for taking time to review and also give your recipe adjustments. Cream is never a bad idea.