Preheat the oven to 350 degrees F. Coat a 9-inch pie plate with cooking spray.
Combine the sugar, buttermilk, biscuit mix, melted butter, vanilla, and eggs in a blender and process until smooth. Pour into prepared pie plate and bake until browned and still a little jiggly (the pie will set as it cools), 30 to 40 minutes.
Let cool for 10 minutes before slicing into wedges. If desired, sift confectioners' sugar or cocoa (or a combo) over the wedges before serving.
Recipe courtesy of Robin Miller, 2007