The moment I returned from a summer vacation to Kaua'i, I was thinking about how to re-create one of the tasty treats I'd had on the trip: Okinawan sweet potato pie. A classic treat on the islands, the pie has two distinct layers: a bottom layer of Japanese purple sweet potato and a top layer of haupia, the classic Hawaiian coconut pudding. I toyed around with the spices in the sweet potato part and found that I liked more subtle flavoring; the haupia is a simple but nice and coconutty. And the two together make a delicious dessert that will fill you with aloha!
Look for the Japanese sweet potatoes at Asian markets that sell produce. The tubers can vary in size from tennis ball-sized to a foot long, but what's most important is that they are firm all around and free of any softer parts that are wrinkly and blemished. I suggest boiling them gently, but feel free to roast them instead. —vvvanessa
1 9-inch by 13-inch pie
Crust and Sweet Potato Filling
plain graham cracker crumbs
unsalted butter, melted and cooled but still liquid, divided
kosher or fine sea salt, divided
large Okinawan purple sweet potatoes (about 2 pounds)
Preheat oven to 325ºF.
Combine the graham cracker crumbs, 1/2 cup of the melted butter, and 1/2 teaspoon of the salt. Mix well until the mixture looks like wet sand. Pour into a 9-inch by 13-inch baking dish and press the crust firmly and evenly into the pan (it only needs to cover the bottom). Bake for 10 minutes and allow to cool slightly.
While the crust is in the oven, start the filling.
Halve the sweet potatoes and place them in a pot with enough water to cover them well. Bring them to a moderate boil and cook them until the point of a sharp knife penetrates the thickest part of the potato easily, which will take anywhere from 15-30 minutes, depending on the size of the potatoes. Remove them from the water and cool until they can be handled easily. Remove the skins, then mash the flesh with a potato masher (smoother is better, but a few lumps won't hurt).
Raise the oven temperature to 400ºF.
Measure out 2 1/2 cups of mashed sweet potatoes into a large bowl. Add in the rest of the ingredients (including the rest of the butter and salt), and whisk them together thoroughly.
Pour mixture into the prepared crust. Bake for 15 minutes. Lower the temperature to 325ºF and cook for 30-35 minutes more, turning the pan once during cooking. The pie is cooked when the center is set and doesn't jiggle when the pan shakes.
Remove from the oven and place on a rack to cool.
While the pie bakes, make the haupia.
In a heavy-bottomed saucepan, combine the ingredients (minus the shredded coconut and macadamias), and whisk together thoroughly to eliminate all lumps. Place over medium-high heat. Stirring constantly, bring to an almost-boil then lower to a simmer. Continue to cook and stir until the mixture thickens, 6-8 minutes. Remove from heat and allow to cool just until it is no longer hot.
Pour the haupia over the cooled pie and spread evenly to cover. Refrigerate until the pudding firms up, at least 3 hours or ideally overnight.
Garnish with toasted coconut flakes or chopped, toasted macadamia nuts. Slice into 15 rectangles, and serve cold or at room temperature.