Buttermilk Silk Pie

Preheat the oven to 3500 F, with a rack in the lower third. Bake the pie shell, gently pricking any air bubbles with a fork, until it is partially baked (it will not take on much color at this point), 8 to 10 minutes. Cool the pie shell on a wire rack; leave the oven on. Meanwhile, in a bowl, whisk together the sugar and cornstarch until there are no bumps. Add the egg, egg yolks, melted butter, buttermilk, vanilla, and salt and mix well. Pour the filling into the partially baked pie crust Bake until the surface is a very pale golden color and the custard is et but still slightly wobbly in the center (the mixture will set up more as it cools; do not overbake), about 40 minutes. Cool the pie to room temperature on a wire rack. Serve at room temperature or slightly chilled.