1) Preheat the oven to 375°F and lightly grease a 9" pie plate.
2) To make the crust and crumb topping: Mix the flour, sugar, salt, baking soda, and cinnamon in a medium-sized bowl. Work the soft butter into the flour mixture with two forks or a pastry blender.
3) Line the pie plate with 2 cups of the crumb mixture, starting with the bottom and pushing the crumbs evenly up the sides of the pan to the top edge. Reserve the remainder of the crumbs for the top of the pie.
4) Bring about 1 cup of water to a boil. You will only need to use 3/4 cup, but some will evaporate.
5) To make the filling: Mix the molasses, syrup, and baking soda; set aside.
6) Add 3/4 cup of the boiling water to the molasses mixture, and stir thoroughly.
7) Pour the molasses mixture over a spoon (to prevent creating a hole in the crust) and into the crust. Sprinkle the remaining crumbs on top.
8) Bake the pie for 25 minutes. The top will be cake-like, while the filling will have a bottom layer that's still gooey. Remove the pie from the oven, and cool completely before serving. Shoofly pie is best served at room temperature with whipped cream.
Yield: one 9" pie, about 8 to 10 servings.