Steps
- Mix 1½ cups of all-purpose flour, ¼ teaspoon of baking powder, and half of ½ teaspoon of table salt. Rub in ¼ cup of shortening and ¼ cup of cold unsalted butter until fully blended.
- Toss with 1 teaspoon of white vinegar and 3 tablespoons of ice water, adding a little more water only if needed to bind. Form a disk, wrap, and chill for 1 hour.
- Preheat the oven to 350°F / 175°C. Roll the dough into a 12in / 30cm circle, line a 9in / 23cm pie pan, crimp the edge, and chill while making the filling.
- Lightly beat 3 large eggs with 1½ cups of granulated sugar, 2 tablespoons of all-purpose flour, and the remaining salt.
- Stir in ½ cup of melted unsalted butter, then ¾ cup of buttermilk and 1½ teaspoons of vanilla extract. Pour into the unbaked crust.
- Bake on the bottom rack for 20 minutes, then on the middle rack for 24-28 minutes, until a thin crust forms and the center barely jiggles. The filling should reach 175°F / 79°C halfway between the edge and center; cool on a rack.