Why It Works
- Macerating apple slices breaks down the fruit’s structure, thus reducing its volume, which means more fruit can fit into the pie.
- Parboiling slices of sweet potato first ensures a tender, supple texture when baked.
- The addition of tapioca starch thickens the fruit juices just enough while ensuring a clean flavor.
I spent several years learning the art of pie making at Four & Twenty Blackbirds, a beloved bakery located in Brooklyn, NY. Come fall, customers swiftly turned their attention to the signature salted caramel apple pie, but I was a steadfast fan of their sweet potato–apple crumble. Inspired by that combination, this pie marries sweet potatoes and apples with a mix of spices—including cinnamon, Chinese five-spice powder, and white pepper—and generously tops it with a punchy almond and thyme-spiced crumble.
For the apples, I took a cue from Stella, who exclusively calls for tart apples (like Granny Smiths) in her old-fashioned apple pie recipe. Combining apple slices with brown sugar and spices and allowing the mixture to macerate for three hours reduces its volume, which means more raw fruit can fit into a single pie. When baked, Granny Smiths hold their shape well, deliver a slightly tart bite, and complement the tender texture of sweet potatoes.
With the sweet potatoes, I tested several methods in order to pinpoint one that delivers a soft, supple texture. First, I tried par-boiling whole peeled sweet potatoes (the same method employed by Four & Twenty Blackbirds), which sometimes resulted in thoroughly tender ones but were more often either inconsistently cooked, with mushy exteriors and raw interiors, or completely overcooked. To shorten the cooking time and improve reliability, I opted to slice the sweet potatoes into smaller pieces that cook through faster and more consistently. The result is crisp-tender pieces that become perfectly cooked once baked.
A couple other notable techniques I tested for the sweet potatoes that didn’t make the cut: Kenji’s method of par-cooking sweet potatoes at low temperatures, which enhances their sweetness, produced ones that were too sweet in the context of this pie; microwaving the sweet potatoes, meanwhile, yielded mixed results—while the technique works well for fully cooking a sweet potato until soft and silky, it's not nearly consistent enough when the goal here is par-cooking.
To finish the pie is a nubby crumble topping, made by combining flour, sliced almonds, sugar, thyme, salt, spices, and a liberal amount of melted butter. The result is a show-stopping pie that not only will be a welcome addition on the holiday table, but pulls off the remarkable feat of satisfying both apple pie lovers and sweet potato pie lovers alike.
- For the Crumble:
- 3 ounces all-purpose flour (about 1/2 cup; 85g), such as Gold Medal
- 1/2 teaspoon Diamond Crystal kosher salt; for table salt, use half as much by volume
- 1/2 teaspoon ground cinnamon
- 1/4 teaspoon ground Chinese five-spice powder
- 2 ounces (1/2 cup; 60g) sliced almonds
- 2 ounces (1/4 cup; 60g) granulated sugar
- 2 ounces (1/4 cup; 60g) light brown sugar
- 2 tablespoons (4g) fresh thyme leaves
- 3 ounces (6 tablespoons; 85g) unsalted butter, melted
- For the Filling:
- 6 ounces (3/4 cup; 170g) light brown sugar
- 1 teaspoon (4g) Diamond Crystal kosher salt; for table salt, use the same weight or half as much by volume
- 3/4 teaspoon ground cinnamon
- 3/4 teaspoon ground Chinese five-spice powder
- 1/4 teaspoon ground white pepper
- 4 medium tart apples (about 2 pounds; 900g), such as Granny Smith (see note)
- 2 medium sweet potatoes (about 1 1/2 pounds; 680g)
- 1 ounce tapioca starch (1/4 cup, spooned; 25g), such as Bob's Red Mill
- Old-Fashioned Flaky Pie Dough, rolled and chilled per directions for a single-crusted pie
For the Crumble: In a medium heatproof bowl, combine all-purpose flour, salt, cinnamon, and five-spice powder.
In a blender, quickly pulse almonds until roughly chopped, about 5 seconds. Add to flour mixture.
In the same blender, combine granulated sugar, brown sugar, and thyme. Process until thyme is finely chopped and evenly incorporated into sugar (the mixture should resemble wet sand), about 30 seconds. Add to bowl with flour mixture, then whisk together until well combined, about 30 seconds.
Pour melted butter over flour mixture. Using a flexible spatula, thoroughly mix until no dry flour remains and a damp, crumbly meal has formed, about 1 minute. Set aside.
For the Filling: In a 1-gallon zipper-lock bag, combine brown sugar, salt, cinnamon, five-spice powder, and white pepper.
Peel, quarter, and core apples. Slice each quarter lengthwise into 1/2-inch thick wedges (you should have about 20 ounces/565g of sliced apples, measuring about 5 rounded cups). Add sliced apples to bag, seal, and shake until coated. Macerate at room temperature, flipping the bag occasionally to distribute the syrup, until apples have lost a third of their volume, at least 3 hours. The apples can be held up to 8 hours in the refrigerator.
Meanwhile, peel then quarter sweet potatoes lengthwise. Slice each quarter crosswise into 1/2-inch thick wedges (you should have about 20 ounces/565g of sliced sweet potatoes, measuring about 4 rounded cups).
Place sweet potatoes in a 3-quart saucepan and cover with cold water. Bring to a boil over high heat, then reduce heat to low to maintain a simmer. Cook until sweet potatoes are tender enough to be pierced with a knife, but not completely cooked through, about 5 minutes. Drain sweet potatoes and run under cold water until cooled to stop cooking. Set aside to let cool to room temperature, about 15 minutes.
Adjust oven rack to lower-middle position and preheat to 400°F (204°C).
When apples are ready, add sweet potatoes and tapioca starch to bag, reseal, and toss to combine. Pour sweet potato and apples, along with accumulated syrup, into the prepared pie shell, gently pressing the slices into a flattish mound.
Evenly distribute crumble topping over pie filling, breaking up any large chunks with your fingers.
Place pie on a parchment-lined half-sheet tray. Bake to an internal temperature of around 195°F (91°C) in the very center, about 1 hour 15 minutes (if crumble topping starts to darken beyond chestnut brown in color, loosely cover pie with aluminum foil for remainder of baking time).
Transfer pie to a wire rack and let cool to room temperature, about 1 hour. Slice and serve.
Tart green baking apples, such as Granny Smiths, hold their shape nicely when baked, which complements the texture of the sweet potatoes and keeps the filling sturdy and thick. Not all types of apples can be substituted here, as some varieties may break down more rapidly in the oven, or not cook through in the allotted time.
Make-Ahead and Storage
The crumble topping can be prepared in advance, then transferred to a zipper-lock bag. Lay flat in the refrigerator until chilled (this prevents it from solidifying into a block), then keep refrigerated in an upright position until needed for up to 1 month.
The sweet potatoes can be par-cooked and then refrigerated in an airtight container for up to 3 days before adding to macerated apples and continuing with the recipe.
Wrapped tightly in foil, the baked pie will keep for up to 3 days at room temperature. Warm leftovers in a 350°F (177°C) oven to restore crumble, crust, and filling.