In a medium bowl, whisk together flour, baking soda, ginger, cinnamon, salt, allspice and nutmeg. Set aside.
Place 4-6 small ramekins or 8-inch baking dish on a baking sheet and grease or spray with baking spray.
In a small bowl, combine 1/2 cup water with 1/2 cup molasses. Stir well and set aside.
In a medium bowl with an electric mixer or the bowl of a stand mixer, beat butter and sugar until creamy, about 2 minutes. Add egg and beat until mixed. Reduce speed to low and add the flour mixture alternately with the molasses mixture. Mix just until blended.
Divide batter between ramekins (or add to baking dish), filling ramekins no more than 1/2 full with batter. Sprinkle with brown sugar (dividing the 6 Tbsp. between your dishes). Combine hot water with melted butter and stir well. Carefully pour over top, dividing between ramekins or adding all to one baking dish. Allow 1/2-3/4 inch clearance at the top of the dish.
Bake in preheated oven until firm and cracked on top and a toothpick inserted in the top half of cake comes out clean, about 35 minutes. Serve warm with a dollop of whipped cream or ice cream.
Be sure to read the "Cook's Notes" in the original post, for more tips, options, substitutions and variations for this recipe!