Cookbook author (and Martha's former colleague!) Virginia Willis always brings a Southern touch to her baking. Here, she takes a traditional chess pie to decadent new heights with the addition of dark chocolate chips and cocoa powder.
Crust: Pulse flour and salt in a food processor to combine. Pulse in butter until mixture resembles coarse meal, 8 to 10 seconds. Pulse in egg yolks.
While pulsing, add ice water, 1 tablespoon at a time. Pulse until mixture holds together as a soft but not crumbly or sticky dough. Shape dough into a disk and wrap in plastic; refrigerate until firm and evenly moist, about 30 minutes.
Lightly flour clean work surface and a rolling pin. Place dough in center of floured surface. Roll out dough, starting in center and rolling up to, but not over the edge. Give dough a quarter turn and continue rolling, repeating quarter turns until you have a disk about 1/8 inch thick.
Transfer dough to a 9-inch pie dish. Gently tuck dough into pie dish, being careful not to stretch or pull dough. Let dough settle into bottom of pie dish. Take a small piece of dough and shape it into a ball. Use ball as a tool to press around bottom edges of pie dish, snugly shaping dough to pie dish without tearing it. Crimp or flute edges as desired. Prick bottom of dough all over with the tines of a fork to help prevent shrinkage during baking. Refrigerate until firm, about 30 minutes.
Preheat oven to 425 degrees. Line dough with parchment, pressing it into corners and edges, then fill with dried beans, rice, or pie weights. Bake until sides are golden, 25 minutes. Remove beans and parchment; continue baking until crust is light golden-brown, 5 minutes more. Reduce oven temperature to 325 degrees.
Filling: In a heatproof bowl set over (not in) a pan of simmering water, melt butter and chocolate. In a separate bowl, whisk eggs until smooth. Add sugar, cocoa, cornmeal, and salt; whisk well to combine. Add butter-chocolate mixture, buttermilk, and vanilla; whisk well to combine. Pour into warm crust.
Bake until set and not wiggling, 45 minutes (cover with parchment-lined foil if pie is getting too dark during the last 15 minutes of baking). Transfer to a wire rack; let cool completely, at least 2 hours.
The pie may puff and crackle during baking, which is fine. It will settle as it cools.