For the crust: In the bowl of a food processor, combine flour and salt by pulsing 3 to 4 times. Add butter and pulse until texture looks mealy, 5 to 6 pulses. Add lard and pulse another 3 to 4 times. Remove lid of food processor and spritz surface of mixture thoroughly with water. Replace lid and pulse 5 times. Add more water and pulse again until mixture holds together when squeezed. Place mixture in a large zip-top bag, squeeze together until it forms a ball, and then press into a rounded disk and refrigerate for 30 minutes.
Heat oven to 425ºF.
Place a 9-inch metal pie pan in the refrigerator to chill.
Remove dough from refrigerator and roll out in the bag until it reaches the edges of the bag and is 10 to 11 inches round. Cut along two sides of the plastic bag, open bag to expose dough on one side, and turn a 9-inch pie pan upside down on the exposed side. Invert the entire thing and gently pull the remaining side of the plastic bag off the dough. Press the dough into the edges around the pan and trim any excess dough. Press the edges of the dough over the lip of the pan. Place in refrigerator for 15 minutes.
Poke holes around sides and into the bottom of the dough. Place a large piece of parchment paper on top of dough and fill with dry beans. Press beans into edges of dough, set on a half-sheet pan, and bake for 10 minutes. Remove parchment and beans, and continue baking until light golden in color, approximately 7 minutes longer. Remove from oven and place on wire rack to cool completely while preparing the filling.
Decrease heat of oven to 350ºF.
For the crumbs: Place the flour, brown sugar, butter, and salt in the bowl of a food processor and process until it forms crumbs. Reserve 1/4 cup and set both aside.
For the filling: Place the baking soda in a medium mixing bowl and pour the boiling water over it. Add the molasses, egg, and vanilla, and whisk to combine. Add the larger amount of crumbs to the molasses mixture and whisk just to combine. Pour this mixture into the prepared crust. Sprinkle the remaining 1/4 cup crumb mixture evenly over the top of the filling. Place pie on the middle rack of the oven and bake until the filling puffs, begins to look dry, and starts to crack slightly, 40 to 45 minutes. Remove from the oven, transfer to a wire rack, and cool completely before cutting.