In a a medium-sized bowl whisk together the flour, brown sugar, cinnamon, nutmeg, and salt. Once combined cut in the butter until the butter is small crumbs.
In a 4-cup capacity glass measuring cup mix the hot water, molasses, a lightly beaten egg and the baking soda and stir well.
Sprinkle 1/3 of the flour mixture into the bottom of the pie crust into an even layer. Pour half of the molasses mix onto the flour. Spread another 1/3 of the flour mixture on top again. Pour the remaining molasses mixture on top. Finish the pie by sprinkling the last 1/3 of the flour mixture on top.
Bake the pie for 10 minutes then reduce the heat to 350°F and bake for another 20 minutes more. Check for doneness. The pie is cooked properly when the middle of the pie is firm when the plate is lightly shaken.
Remove from the oven and let the pie cool and set for at least an hour before slicing and serving.
Notes
This is a dense pie that holds together so well that it could be eaten by hand! It has a gooey cake-like interior.