Preheat the oven to 350°F. Spray a 9x5-inch loaf pan with gluten-free nonstick cooking spray and line with parchment paper.
In a medium bowl, whisk together the gluten-free flour, xanthan gum, baking powder, baking soda, salt, granulated sugar, cinnamon, nutmeg, and cloves. Stir in nuts, raisins, chocolate chips, etc. if using.
In a separate large bowl, add the pumpkin puree, eggs, light brown sugar, oil, milk, and vanilla. Whisk to combine and then whisk in the sourdough discard until completely incorporated.
Pour the dry ingredients into the wet ingredients and mix until all the flour is combined and moistened. Transfer the batter to the prepared baking pan.
Bake for 60-75 minutes or until a cake tester or toothpick comes out clean. This bread takes longer to bake than traditional pumpkin bread. If your bread starts to brown too much on top before it's done, loosely cover it with foil.
Once the bread is done, cool in the pan for 20 minutes, then remove it from the pan, discard the parchment paper, and cool on a wire rack. For best results, cool completely before slicing.
Keep the bread wrapped tightly in plastic wrap at room temperature for up to 3 days. To freeze, wrap tightly in plastic wrap then freeze in a freezer-safe bag for up to 3 months.
My sourdough starter/discard is made with 100 percent hydration (equal parts flour and water). If your starter is made with different proportions of flour and water, it will affect the outcome of the bread. Starters made with less water may produce a dry bread and starters made with more water will produce a loaf that is too wet or will not bake through properly.Here's a quick sourdough starter recipe/feeding schedule:
Day 1: Add 25 grams flour and 25 grams water to your glass jar. Mix well and scrape down the sides the best you can.
Day 2: No discard. Add 25 g flour and 25 g water.
Day 3-6: Stir the starter and discard all but 25 g of the starter. Add 25 g flour and 25 g water. Mix well and scrape down the sides the best you can.
Day 7-10: Stir the starter and discard all but 25 g of the starter. Add 50 g flour and 50 g water. Mix well and scrape down the sides the best you can.
Day 11-14: Stir the starter and discard all but 25 g. Add 75 g flour and 75 g water. Mix well and scrape down the sides the best you can.
After day 14: You can continue to maintain this feeding schedule if you plan on baking with it soon or you can now store and maintain your starter in the refrigerator.