• Add the butter, granulated sugar, brown sugar, pumpkin puree, egg, sourdough starter and vanilla to a large mixing bowl and whisk together until light and fluffy.
• Now add all of the dry ingredients - all purpose flour, pumpkin pie spice, salt, baking soda and rolled oats and gently mix together to form a sticky dough. It will be fairly wet and that's ok.
• Cover the bowl with plastic wrap to stop it drying out and place into the fridge for a minimum of 2 hours (and up to 48 hours). These cookies taste best when fermented overnight.

When You're Ready to Bake

• Preheat your oven to 190ºC (375ºF).
• Using a large spoon or cookie scoop, scoop balls of dough onto the cookie sheets lined with parchment paper. These sourdough oatmeal cookies will spread so make sure you leave at least 2" between each dough ball (see notes for sizing and baking times).
• Place trays into the oven and bake for around 10 minutes at 190C (375F) or until the edges of the cookies are starting to brown but the middles are still soft. Don't let them overcook!
• Remove them from the oven and allow to cool on the cookie tray for around 10 minutes before placing them on a wire rack to fully cool.
• Once cool, they will have crispy edges and a soft, chewy centre - YUM!
• To create the glaze, mix together the powdered sugar and water until it's smooth and glossy. Use a piping bag to drizzle over the cold cookies.