In a heavy saucepan combine the molasses, brown sugar, ginger, cinnamon, allspice, and cloves and bring to a boil over medium heat, stirring occasionally. Remove from the heat. Stir in the baking soda and then the butter, 3 pieces at a time, letting it melt before adding more. When all the butter is added and melted, add the egg and stir to combine. Let cool slightly and then stir in 4 cups of flour and the salt.

Preheat the oven to 325 degrees. Line baking sheets with parchment paper. Transfer the dough to a lightly floured surface and knead, dusting with the remaining flour as needed to prevent sticking. Knead for 30 seconds to 1 minute, until the dough is soft and easy to handle. Cut the dough in half; wrap half of it in plastic and keep at room temperature. Roll out the other half into a 14-inch round about 1/8 inch thick on a lightly floured surface. Cut out as many cookies as possible and transfer to baking sheets, set about 1 inch apart. Bake cookies for 12 to 14 minutes, turning the sheet trays halfway through baking. Let cool on the tray for 5 minutes, then transfer to wire racks to cool completely. Meanwhile, roll out, cut, and bake the remaining dough. Decorate the cool cookies (make sure they are completely cool before you decorate) with Royal Icing and let dry for about 1 hour before storing in an airtight container. Or store the cookies in an airtight container at room temperature for up to 5 days before decorating.