Thick and sweet as a Southern drawl, chess pies were born during a time when dessert depended on the creativity of the cook equipped with only farm staples – eggs from the henhouse, cream from the morning milking, home-churned butter kept cool in the springhouse, and sugar. If you have never baked a chess pie, you may notice that the filling puffs as it bakes and then slowly begins to fall. It is not unusual for it to crack on top, but to minimize the chances of cracking, let it cool slowly and away from drafts.
Preheat oven to 325 degrees. Press unbaked pastry shell into a 9-inch or 9-½-inch pie plate. Stir butter and chocolate in a small heavy saucepan over low heat until melted and smooth. Remove from heat; cool 10 minutes.
Whisk eggs and sugar in a medium bowl to blend. Whisk into chocolate mixture, then add bourbon, vanilla, and salt. Stir in pecans. Spoon mixture into pastry shell. Bake about 40 minutes, until edges of filling puff and begin to crack, and center is just set. Transfer pie to rack and cool completely. Serve with whipped cream or ice cream.