To make the piecrust:Place the dry ingredients in the bowl of a food processor fitted with a metal blade. Pulse to combine. Add the butter and pulse until crumbly. Add the water and vanilla. Pulse until the dough just comes together. Form into a disk. Cover tightly with plastic wrap and chill 15 minutes. Roll the dough out on a floured surface into a 12-inch circle. Fit the dough into a 9-inch pie plate. Refrigerate until needed.
To make the filling:Preheat oven to 350°F. In a large bowl, whisk together the first 8 ingredients. Stir in the pecans. Scatter the chocolate over the prepared piecrust and cover with the filling. Bake until the center is set, 45 to 50 minutes. Let cool completely. Serve with the cream, if desired.