Combine molasses, 3/4 cup hot water, and soda dissolved in another 1/4 cup hot water. Mix well.
Stir in crumbs (those not set aside). Pour the resulting filling into pie shell.
Top with the reserved 1/2 cup crumbs.
Bake at 375 for 35 minutes. Serve pie warm or cool in small slices as it is rich. You may serve it with ice cream or whipped cream.