Southern Sweet Potato Pie

From the garden

• 2 lb sweet potatoes, scrubbed, skins left on · about 3 medium roots, to yield 2 cups of mash

From the pantry

• 1¼ cups all-purpose flour · for the crust, plus more for rolling
• 12 tbsp butter, 8 cold and cubed, 4 softened · the cold butter is for the crust, the softened for the filling
• ¾ cup granulated sugar
• ¼ cup brown sugar · packed
• 1 tsp ground nutmeg
• ½ tsp ground cinnamon
• 3 eggs, lightly beaten
• ½ cup whole milk · evaporated milk is the more traditional choice
• 2 tsp vanilla extract
• ¾ tsp salt · half for the crust, half for the filling

1. Heat the oven to 400°F. Bake the whole sweet potatoes on a lined sheet 50–60 minutes, until they slump and dark syrup leaks from the ends. Baking rather than boiling is what concentrates the sugar.
2. Rub the cold butter into the flour and half the salt until it looks like coarse crumbs with some pea-size pieces, then stir in ice water a tablespoon at a time (about 4) until it just holds together. Press into a disk and chill 30 minutes.
3. Roll the dough into a 12-inch round, fit it into a 9-inch pie plate, crimp the edge, and chill 15 minutes. Line with foil and pie weights and blind bake at 400°F for 18 minutes, then lift the foil out.
4. Split the hot potatoes, scoop the flesh into a bowl, and beat it with the softened butter while still steaming. Whip until no strings remain, pushing it through a sieve if any do, and measure 2 cups.
5. Beat in both sugars, the spices, and the remaining salt, then the eggs and the milk. Keep beating a full minute: air whipped in now is what gives this pie its lift over a dense pumpkin custard.
6. Pour into the warm shell and bake at 350°F for 40–50 minutes, until the top has puffed, cracked a little at the edge, and the center barely moves when the plate is nudged.
7. Cool on a rack 2 hours before cutting, letting the filling firm and the surface settle. Serve at room temperature, plain or with whipped cream.