There is no need to preheat the oven for these cookies when you mix the dough because the dough needs to ferment in the fridge for at least a few hours before they are shaped and baked.
In a small bowl, combine the cinnamon, nutmeg, ginger, all spice, black pepper, cloves, salt and baking soda and set aside.
In a medium sized mixing bowl, add the butter and brown sugar and whisk until well combined.
Now, to the butter and brown sugar add the vanilla extract, egg, molasses and sourdough starter. Whisk until the batter is light and fluffy. The sourdough starter will make the mixture seem a little marshmallowy.
To this bowl, add the flour and spices you combined earlier and mix with a spatula to form the cookie dough. Cover with plastic and place into the fridge to ferment and firm up. You can leave the cookie dough in there for up to 24 hours, but a minimum of 2 hours is sufficient. The longer you leave it, the longer your sourdough starter has to do it's job.