This sweet potato pie is sweetened solely with maple syrup and has a slight butterscotchy flavor thanks to the fragrant browned butter. I roast the sweet potatoes (boiling them can make for a pie with a little more moisture than I ultimately want) but you can certainly use canned sweet potato or even pumpkin here if you’d prefer. The one step not to skimp on is pre-baking the pie shell: whenever you’re working with a custard (or wet) filling, you really want to do this so your bottom crust won’t end up soggy.
Make the pie dough: Whisk both flours, salt and sugar together in a medium bowl. Using a pastry blender (or your fingertips), cut the butter into the flour, working quickly, until mostly pea-size bits of butter are left. Drizzle in the cider vinegar and 2 tablespoons of ice water and stir with a fork or your fingers. Add more of the ice water mixture, 1 tablespoon at a time, until the dough comes together into more of a uniform ball. It’s ok if there are some dry, mealy bits and great if there are bits of butter still visible. Test if it’s done by squeezing and pinching the dough with your fingertips to see if you can gather it together. Shape into a flat, chubby disk, wrap in plastic wrap, and refrigerate for at least 1 hour and up to 1 day.
Roll and bake the pie shell: When you’re ready to roll out your crust, take out the dough about 10-15 minutes before working with it so it has a chance to soften up just a bit and become more pliable and easier to work with. Then work quickly to roll out the dough on a lightly floured surface until it’s about 11-12 inches round. Carefully transfer to a 9-inch pie plate and nestle gently into place. Leave 1-inch of overhang (if there’s a great deal of overhang, trim), then fold edges under and crimp.
Preheat the oven to 375 F. Prick the bottom of the pie shell a few times. Line with parchment paper or aluminum foil and fill to the top with pie weights or dried beans. Bake for 20 minutes, or until lightly golden. Remove pie weights or beans along with parchment or foil and bake for an additional 8 minutes, or until the shell is nice and dry on the bottom.
Make the filling: Preheat oven to 400 F. Prick sweet potatoes with a fork, set on a baking sheet and bake for one hour, or until soft. When finished cooking, remove sweet potatoes from the oven and reduce the temperature to 350 F.
In a small light-colored saucepan, melt the butter over medium heat, stirring occasionally with a rubber spatula to encourage even cooking. Cook until butter begins to foam, about 4-5 minutes. Continue cooking until the foam subsides and little brown bits appear at the bottom of the pan, smelling fragrant and nutty. Pour butter into a heatproof bowl, remove from heat, and stir for 1-2 minutes to allow it to cool. Set aside.
When cool enough to handle, slice sweet potatoes in half and scoop out the flesh. Discard the skin and place sweet potatoes in a food processor fitted with a metal blade. Puree until smooth (should yield about 1 2/3 cup). Add the eggs, maple syrup, heavy cream, sour cream, vanilla extract, flour, cinnamon, ginger, cloves and salt and pulse a few times to combine well. Slowly stream in the slightly-cooled brown butter.
Pour the mixture into the prepared pie shell and bake until set, about 55-60 minutes. The pie is finished when the edges are completely set and the center is no longer liquid but still a touch jiggly (it will continue to set after it comes out of the oven). Cool on a wire rack for at least 2 hours before serving. Serve warm or room temperature with whipped cream if you’d like.