Despite all the molasses, this pie is rich, rather than overly sweet.
You only need a bottom crust, not a top crust. Use an 8 or 9 inch (20 or 23 cm) pie pan. The bottom of the filling may still be slightly moist when you take it out of the oven, but it will set. Optional: flavour the crumble with 1/8 teaspoon each of any or all of the following: ground ginger, ground nutmeg, ground cloves.