Purple Sweet Potato Pie

Sweet, caramelized Purple Sweet Potato Pie uses brown butter to add a delicious nuttiness to the warm-spiced filling. Nested in a flaky pie crust and piled with meringue toasted to marshmallow goodness.

Posted: 10/13/2020; Updated: 10/26/2021

First, allow me to re-mention the addition of brown butter in the sweet potato filling which gives the pie a little something extra that you can’t quite put your finger on, but you KNOW it’s there.

Also, the brown sugar in the filling provides a rich caramel flavor and the addition of the warm spices make it feel like autumn in your mouth!

This southern classic is thick and dense, yet oh so creamy and leaves you going back for just one more bite. I will never tire of this pie. Or pies or tarts in general. Pastry is life.

This recipe is made with my all-butter pie crust - take a look through before getting started. It has all the tips and tricks you'll need to master a homemade, super flaky pie crust!

What are Purple Sweet Potatoes

Purple Sweet Potatoes, also known as an Okinawan Sweet Potatoes, Hawaiian Sweet Potatoes, Japanese Sweet Potatoes, or Purple Yams have a beautiful purple flesh and light to medium brown skin. They are creamy and have a better depth of flavor than orange sweet potatoes, and taste more of honey! They are also incredibly vibrant - though the brightness inside each potato can vary.

While they are sometimes called purple yams, they are not a yam. Yams are drier and have a higher starch content. While all names and versions are similar, you should be looking for either Okinawan, Japanese, or Hawaiian Sweet Potatoes.

When purchasing, be careful not to be tricked by a purple-skinned sweet potato, which actually has a yellow/white flesh. You want brown skin and purple flesh! My local, favorite Asian market carries Purple Sweet Potatoes, but I have also found them at Trader Joe’s and Whole Foods from time to time.

My suggestion would be to call ahead to a few stores to see if they carry them instead of going on a wild goose chase. If you can’t find purple sweet potatoes in your area, you can absolutely make this with normal orange sweet potatoes.

Ingredients & Tools

• Purple sweet potatoes. We talked about this just above, but start calling around to figure out who has the goods!
• Unsalted butter. You'll need this in two forms: 1) freezing cold for the pie crust, and 2) cooked down into brown butter, which is a non-negotiable here! Check out my How to Brown Butter post for all the tips on how to do this and how long to cook it for.
• Heavy whipping cream and milk. Both are needed here.
• Eggs. Two whole for the filling and three whites for the meringue.
• Sugars. Light brown for the sweet potato filling, granulated for the Swiss meringue.
• Spices. Ground cinnamon, nutmeg, ginger. This is a sweet potato pie, after all.
• Vanilla paste or extract. Just get the vanilla paste. Especially for meringue, it's really the second best option to real vanilla beans (which are expensive).
• Food processor or pastry cutter. This is for the pie dough, I pretty much always use my food processor for my crust recipe.
• Pie weights or dried rice or beans. This is necessary to par-bake the crust and prevent the sides from slouching. Do not eat the rice or beans after using - these are now your new pie weights (store in a bag or container). If you you don't have any of these items, add a piece of parchment paper over the crust and place another pie dish on top.

How to make the Purple Sweet Potato Pie

Pie crust

STEP 1: Make the All-Butter Pie Crust . Be sure that your butter is super cold and don't over blend it. Visit the post write up for all the details on how to do this. Hydrate the dough in the fridge for 2 hours. 

STEP 2: While the crust is hydrating, wash and pierce 4-5 purple sweet potatoes and bake in a 400℉ oven for about one hour or until the flesh is very soft. Remove from the oven, slice open to cool, then scoop out the flesh and mash diligently with a fork until completely blended. You can also pass this through a ricer or sieve to get rid of any fibrous pieces, but that is optional.

STEP 3: Once the dough is hydrated, remove it from the fridge to stand at room temperature for 15 minutes. Lightly flour your work surface and roll out the dough until it’s about ⅛” - ¼” thick. Transfer to the pie dish, trim and crimp. 

Freeze the crust for 15 minutes, dock all over with a fork, then fill with parchment paper and pie weights and bake in a 375℉ oven for 20 minutes. Remove the weights and bake for another 10-15 minutes, then remove to a wire rack to cool.

Sweet Potato Filling

STEP 4: While the crust is baking, make the brown butter and transfer to a heatproof bowl. Follow my How to Brown Butter post for tips on how to do this. 

STEP 5: Combine the mashed purple sweet potato, brown butter, heavy cream, milk, brown sugar, beaten eggs, cinnamon, nutmeg, ginger, salt, and vanilla in a large bowl with a whisk until fully combined. 

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Pour into the prepared pie crust and bake for 40-50 minutes or until the pie is set. It will look slightly puffy on the edges and may still have a slightly jiggle in the center, but it should not be sloshy. 

Cool at room temperature for 2 hours, then transfer to the fridge for 2 hours to finish cooling and setting. 

STEP 6: Once the pie is completely chilled, remove it from the fridge to come back to temperature as you begin making the Swiss meringue topping.

Marshmallow Meringue

This soft meringue topping is made with the Swiss method, which means the egg whites are first cooked with sugar before whipping. Because this method stabilizes the whites, no cream of tartar is needed for this meringue. It's also a much smoother, silkier texture and also doesn't require baking.

STEP 1: Start by separating the yolks from the whites. Don't get any yolks in the whites or you’ll have to start over (it won’t whip up properly). Then, prepare a double boiler by filling a saucepan with about 2 inches of water and turn to high heat. Add a heat proof bowl over top that fits securely. You don’t want any of the water touching the bottom of the bowl.

STEP 2: To the bowl, add the egg whites, sugar, and salt and whisk to combine. Continue lightly whisking until the mixture is rather warm and the sugar granules have dissolved. Check this by rubbing your fingers together in the mixture. If you can still feel sugar granules, continue cooking. It will be rather warm to the touch, but not overly hot.

Whipping the meringue

STEP 3: One the mixture is ready, add it to the bowl of a stand mixer fitted with the whisk attachment and whip on medium speed for about a minute. Turn to high speed and whip until stiff peaks form and the meringue gets caught in the middle of the whisk. The peak of the meringue should stand up to a point when you pull the whisk out. Once the meringue hits stiff peaks, add the vanilla then mix on high speed once more to combine.

Add all of the meringue to the middle of the pie and keep as much height as possible in the center. Use the mouth of a large spoon to dip it into the meringue, then pull up and twist to get nice swoops and peaks.

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STEP 4: Use a kitchen torch to toast the meringue. This is really the best and most reliable method. If you don't have a torch, carefully broil in the oven, turning the pie to brown it as evenly as possible.

Storing and Freezing

Store the pie in the fridge for three days. I like to cover any exposed sides after slicing with plastic wrap, but otherwise, it doesn't need to be covered. Bring the slices or pie to room temperature before eating.

To freeze, wrap the cooked pie in plastic wrap and foil and freeze for one month. Thaw uncovered in the fridge, bring to room temperature, then prepare and add the meringue.

Best Tips

• In my tests, the color came out differently each time, depending on how bright the flesh was in each potato. If yours is lacking a bit of color, simply add a touch of ube powder or purple food coloring to help her shine bright.
• I prefer to pass my sweet potatoes through a sieve. I've found that Japanese purple sweet potatoes are a bit stringier so the texture of the pie benefits the removal of any fibrous pieces.
• Add your pie to the lower third of the oven for the final 15 minutes. This helps to ensure the bottom of the crust is fully baked.

Other Recipes to Try

• Banoffee Cream Pie
• Peach Frangipane Galette (you can make this with pears!)
• Cinnamon Panna Cotta Tart
• Chocolate Espresso Tart

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Be sure to tag me on Instagram @thecozyplum! I can't wait to see your creations. For more ideas, follow me on Pinterest.

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