PreparationMake pie shell: Roll out dough on a lightly floured surface with a lightly floured rolling pin into a 12-inch round and fit into a 9-inch pie plate. Trim edge, leaving a 1/2-inch overhang. Fold overhang under and lightly press against rim of pie plate, then crimp decoratively. Lightly prick bottom all over with a fork. Chill until firm, at least 30 minutes (or freeze 10 minutes). Preheat oven to 375°F with rack in middle. Line shell with foil and fill with pie weights. Bake until side is set and edge is pale golden, about 20 minutes. Carefully remove weights and foil and bake shell until golden all over, 10 to 15 minutes more. Make Buttermilk filling: Reduce oven to 350°F. Whisk together filling ingredients and pour into shell. Bake until set but still slightly wobbly in center, about 45 minutes. Cool completely, about 1 1/2 hours. Make shoofly filling: Cook molasses, sugar, eggs, flour, and salt in a 3- to 3 1/2-quart saucepan over medium heat, whisking constantly, until it begins to simmer and thickens. Dissolve baking soda in hot water, then whisk into molasses mixture (it will bubble up). Pour over cooled buttermilk layer, spreading evenly. Cool until set, about 30 minutes. Cooks' note:Pie can be made 1 day ahead and chilled.
PreparationMake pie shell: Roll out dough on a lightly floured surface with a lightly floured rolling pin into a 12-inch round and fit into a 9-inch pie plate. Trim edge, leaving a 1/2-inch overhang. Fold overhang under and lightly press against rim of pie plate, then crimp decoratively. Lightly prick bottom all over with a fork. Chill until firm, at least 30 minutes (or freeze 10 minutes). Preheat oven to 375°F with rack in middle. Line shell with foil and fill with pie weights. Bake until side is set and edge is pale golden, about 20 minutes. Carefully remove weights and foil and bake shell until golden all over, 10 to 15 minutes more. Make Buttermilk filling: Reduce oven to 350°F. Whisk together filling ingredients and pour into shell. Bake until set but still slightly wobbly in center, about 45 minutes. Cool completely, about 1 1/2 hours. Make shoofly filling: Cook molasses, sugar, eggs, flour, and salt in a 3- to 3 1/2-quart saucepan over medium heat, whisking constantly, until it begins to simmer and thickens. Dissolve baking soda in hot water, then whisk into molasses mixture (it will bubble up). Pour over cooled buttermilk layer, spreading evenly. Cool until set, about 30 minutes. Cooks' note:Pie can be made 1 day ahead and chilled.