In a medium bowl, stir the baking soda into hot water until dissolved. Mix in molasses and let cool slightly.
In a large bowl, cream together butter, shortening, and sugar. Add salt and spices; mix well.
Pour the molasses mixture into the creamed mixture and stir until combined.
Gradually add flour, mixing until a dough forms. Divide into two portions, wrap in plastic, and chill overnight.
Preheat oven to 375°F. Roll out dough on a floured surface to 1/4-inch thickness. Cut with a round cutter.
Place on parchment-lined baking sheets and bake for 10-12 minutes. Let cool on a wire rack.