Preheat the oven to 375 degrees F (190 degrees C).
Dissolve baking soda in molasses in a medium bowl; stir until it foams. Stir in boiling water and pinch of salt. In a separate bowl, mix flour, cinnamon, brown sugar, and butter into crumbs.
Pour 1/3 of the molasses mixture into unbaked crust. Sprinkle 1/3 of the crumbs over molasses mixture and continue alternating layers, finishing with the crumbs on top.
Bake in preheated oven until crust is light brown and crumbs are golden on top, about 30 minutes.
Classic Shoofly Pie · Dinner Match Lab | Dinner Match Lab