Pulse the oats in a food processor about 10-12 times, until you have the oats in a variety of texture - some fine and some coarse.
In a large bowl cream together the brown sugar, granulated sugar, and butter until light and fluffy, about 5-7 minutes.
Mix in the eggs one at a time.
Add in the starter and vanilla and mix well.
In a second medium bowl, whisk together the flour, oats, baking soda, salt and spices.
Gradually add the dry ingredients to the wet. The dough should be soft and sticky.
Chill the cookie dough for 45 minutes in the fridge before baking.
Bake the cookies
Preheat the oven to 350.
Using a cookie scoop, drop the dough 3” apart onto parchment paper lined baking sheets. You might only get 8-9 cookies per sheet, and that's perfect!
Press each cookie slightly to flatten.
Bake until soft but set, 11-12 minutes. The edges should be light browned and the centers look very soft.
Cool on the pans for 5 minutes.
Transfer to a wire rack to cool completely.
Mix the icing.
In a medium mixing bowl, add the confectioners sugar, vanilla and 1 Tablespoon of milk. Use a fork to stir the ingredients together as much as you can (it won’t come together fully because there isn’t enough liquid).
Slowly, add just enough extra milk to make a very thick icing. It should not be a frosting, it should be just thin enough that it drizzles off the cookie.
Dip the tops of the cookies lightly into the icing.
Allow to set on a wire rack.
Notes
Store these cookies on the counter in a covered container for 3-4 days.This recpe uses a 100% hydration sorudough starter. It can be active or discard, and you can feed it with any flour and still use it in this recipe.