Instructions

• Preheat the oven to 350°F (180°C).
• Roll out the all-butter pie crust and fit it into a 9-inch pie dish. Crimp the edges, cover loosely, and place the crust in the refrigerator while you prepare the filling.
• Place the peeled and cubed sweet potatoes in a large saucepan and add enough cold water to cover them by about 1–2 inches.
• Bring the water to a boil over high heat, then reduce to a simmer and cook the potatoes for 10–15 minutes, or until fork-tender.
• Drain the potatoes well and return them to the warm (off-heat) pan. Add the 1/4 cup (60 g) unsalted butter and mash with a potato masher or potato ricer until there are no large chunks.
• Add 3/4 cup (150 g) granulated sugar, 1/2 teaspoon ground cinnamon, 1/2 teaspoon ground nutmeg, and 1/4 teaspoon salt to the mashed potatoes and stir until combined.
• Let the potato mixture cool until it is warm but not hot (so it will not cook the egg). Stir in 1 large egg and 1/2 teaspoon pure vanilla extract until evenly incorporated.
• In a small bowl, whisk together 2 teaspoons baking powder and 3 tablespoons whole milk. Add this to the sweet potato mixture and stir until smooth. If you prefer a very smooth filling, press the mixture through a fine mesh sieve.
• Pour the filling into the chilled pie crust and smooth the top.
• Bake on the center rack for about 50 minutes, until the filling is set around the edges and only slightly jiggly in the center. (Alternatively, check that the center reaches at least 175°F / 80°C with an instant-read thermometer.)
• Remove the pie from the oven and place it on a wire rack to cool. Let the pie rest at room temperature for at least 2 hours before slicing.
• Serve slices with optional whipped cream and a light sprinkle of ground nutmeg or cinnamon.