Add cut up butter to a large bowl. Set aside.
In a large saucepan, combine brown sugar, molasses, ginger, cinnamon and cloves. Heat over medium heat, stirring, until the mixture comes to a gentle boil. Add baking soda and mix to combine.
Quickly and carefully pour the hot mixture over the butter in a large mixing bowl. Stir until the butter is completely melted (the mixture will look glossy and slightly foamy.) Stir in the beaten egg until fully combined.
Gradually add sifted flour, starting with 3½ cups, mixing until a dough forms that can be kneaded. Knead until smooth, adding up to 4 cups of flour total.
Cover and refrigerate the dough until firm (at least 3-4 hours, or overnight for best results).
Preheat oven to 350 degrees F.
Roll dough out on a lightly floured surface until thin. Cut with Christmas cookie cutters and place on greased baking sheets.
Bake for 8–10 minutes, just until set. Cookies will crisp up as they cool, so don’t overbake.
Mix powdered sugar with water, adding a little at a time, until you reach a spreadable icing consistency. Decorate cookies with icing, sprinkles, or keep them plain.