This Okinawan sweet potato haupia pie is one of my favorite Hawaiian desserts. Most recipes I’ve seen use either a shortbread or pie crust base. I wanted to simplify my life a little, so I used an easy graham cracker crust instead. My recipe uses an 8×8″ square baking tin to make pie bars, but you could easily double the recipe for a 9×13″ dish or even your standard 9″ pie.
What is Okinawan Sweet Potato?
Okinawan sweet potato is a type of sweet potato that has a light brown skin with vibrant purple flesh. When cut open raw, the color is a light purple with streaks of white, but when cooked it turns a deep violet shade. They have a very mild, sweet flavor and a slightly dry, but smooth texture, similar to other sweet potatoes. According to botanical websites, Okinawan sweet potato is part of the morning glory family, and its scientific name is ipomoea batatas. In Okinawa, they are also called “beni imo.”
Lately, Okinawan sweet potatoes have become somewhat popular due to trending documentaries about Blue Zones. These purple sweet potatoes have been shown to have many nutrients, which partially contribute to the long life span of Okinawan centenarians.
Where to Buy Okinawan Sweet Potatoes
Okinawan sweet potatoes are common in Okinawa (obviously) and Hawai’i, but can be very expensive to buy in the mainland US and other areas. I’ve found Okinawan sweet potatoes at my local Japanese and Korean markets, sometimes sold for over $5 a pound!
Okinawan Sweet Potato Substitute
If you can’t find Okinawan sweet potatoes at a reasonable price, you may be able to find other purple sweet potatoes that work as a substitute. The Molokai sweet potato grown by the Decoite family in Molokai, Hawai’i is a purple sweet potato with purple skin and deep purple flesh that is similar to the Okinawan sweet potato. You can also find this kind of purple Hawaiian sweet potato under the brand name “Stokes,” which is grown in North Carolina. These kinds of purple sweet potatoes are much more easily found in the US mainland and are often sold for $3 a pound or less.
What is Haupia?
Haupia is another Hawaiian dessert. It’s made from coconut milk and is sort of similar to a coconut pudding or jello. You can eat it on its own (see my recipe here) or as a layer in other desserts like this pie! I love it in my chocolate haupia pie recipe.
Tips and Tricks for Making Sweet Potato Haupia Pie Bars
Overall, the recipe is fairly easy! You need to make a basic graham cracker crust, then layer the sweet potato filling on top, and then bake. The haupia layer is cooked over the stove and poured on top of the baked sweet potato. The whole thing gets chilled in the fridge. The only time consuming part may be making sweet potato puree.
Different Ways to Make Purple Sweet Potato Puree
I have never seen purple sweet potato puree sold in a can, at least not on the mainland, so you’re going to have to make this from scratch. You’ll need one or two potatoes, depending on how big they are. As always, it’s better to have too much than too little. Anyway, you have some options for how you want to cook your sweet potatoes. You can:
- Poke them with a fork and stick them in the microwave for 5 minutes per side or until they get soft
- Bake them at 425 degrees F until they get soft (if you peel and cut them into 1 inch chunks beforehand it’ll only take about 25 minutes)
- Peel and cut them into chunks, then boil until soft (20-30 minutes)
- Peel and put in the InstantPot steamer for 15 minutes high pressure
- Wrap in foil and roast them on a grill until soft (could be 30-40 minutes)
So, take your pick! It really doesn’t matter how you cook them, as long as in the end, you get a nice soft purple sweet potato. Mash up the inside to get a puree consistency or stick it in a food processor/blender for a few pulses.
More Hawaiian Dessert Recipes
Looking for more easy dessert recipes from Hawai’i? Check these out:
- Haupia (Hawaiian Coconut Pudding)
- Chocolate Haupia Pie
- Easy Homemade Mochi (Chi Chi Dango)
- Honolulu Cookie Company Copycat Recipe
- Almond Jello Recipe (Almond Float)
Okinawan Purple Sweet Potato Haupia Pie Bars
Equipment
- 8×8" baking pan
Ingredients
For Graham Cracker Crust
- 1 1/4 cup graham cracker crumbs
- 5 tbsp melted butter
- 1 pinch salt
For Sweet Potato Filling
- 1 cup purple sweet potato puree 180g, from about 1-2 sweet potatoes
- 6 tbsp sugar
- 1 egg
- 1/4 cup heavy cream or half and half
- 1 pinch cardamom optional
- 3 tbsp melted butter
- 1 tsp vanilla extract
For Haupia
- 1 12 oz can coconut milk
- 3 tbsp sugar
- 3 tbsp cornstarch
- 1/4 cup water
Instructions
Make the Graham Cracker Crust
- Preheat oven to 350 degrees F.
- Mix graham cracker crumbs, butter, and salt
- Press crumbs firmly onto the bottom of a greased 8×8" square baking pan
- Bake in the oven for 10 minutes while you prepare the sweet potato filling.
Purple Sweet Potato Filling
- Cook your sweet potatoes to make a puree: you can do this in the microwave, in the oven, or by boiling – however you would normally make a baked or roast potato. I typically use the microwave: poke holes in your sweet potatoes with a fork, cover, and microwave for 6-7 minutes or until you can very easily pierce through the sweet potato. Peel the skin off the potatoes and mash the insides. You can do this a few days ahead of time and save the puree in the fridge.
- Take one cup of sweet potato puree and mix with the sugar, egg, heavy cream, cardamom, melted butter, and vanilla extract.
- Spread the filling over the graham cracker crust. It will be a thin layer.
- Bake until set – about 20 minutes, or until a toothpick poked in the center comes out clean. Then set your pie to cool in the fridge.
For the Haupia
- While your baked sweet potato layer is cooling, make the haupia.
- Mix sugar, cornstarch, and water in a separate bowl to make a slurry.
- Pour can of coconut milk in a pot and heat on stovetop.
- When the coconut milk is just starting to bubble, pour in your cornstarch slurry very slowly while continuously whisking the hot coconut milk in the pot. It's important to keep stirring to avoid lumps.
- Cook the haupia, continuously whisking, until the mixture has thickened to a pudding like consistency. Do not let the mixture boil, but a few bubbles are okay.
- Take the haupia off the heat. Then, very gently spread over the purple sweet potato filling.
- Place the pie into the fridge to let the haupia layer set. I like to leave it uncovered in the fridge until the top has become dry to the touch, then I cover with plastic wrap.
- When the pie has fully cooled and the haupia is set, you can cut it into squares to serve.
Notes
- You can double the sweet potato portion of the filling if you like extra thick pie bars and lots of sweet potato. The photos in this post reflect a single portion of the filling. My Instagram video of me making this recipe uses a double portion.
- If you can’t find Okinawan sweet potato or they’re too expensive, you can use Molokai sweet potato, which is purple on the outside and inside. The Stokes sweet potatoes brand are an example of a Molokai sweet potato.
- You can also make this recipe in a 9×9″ square baking dish, although the layers will be slightly thinner.