Preheat the oven to 350°F.
Line with parchment paper a 8X4 inches loaf pan. I usually use a 8X4, but it can be done in a 9X5 inches, it will only affect the final size of the cracker.
In a large bowl, mix the milk, sourdough discard and pumpkin puree.
Add the brown sugar, cinnamon, ginger, nutmeg, salt and thyme and mix to combine.
Add the sunflower seeds, chopped pecans and dried cranberries and mix until incorporated into the batter.
In a medium bowl, mix both the all-purpose and whole wheat flours, rolled oats and baking soda.
Add the flour mixture on the batter and stir until everything is well combined.
Distribute the batter evenly into the lined loaf pan.
Bake for 25 to 30 minutes, or until you insert a toothpick into the middle and it comes out clean.
Let the loaf cool completely on a rack before wrapping it with plastic wrap. Freeze for 40 minutes. If you freeze it for longer than 2 hours, let it thaw for 40 minutes to 1 hour before cutting. If the middle is totally frozen, it’s harder to slice the crackers.
Preheat the oven to 250°F.
Unwrap loaf. With a bread knife or any serrated knife, slice the loaf as thinly as you can. Aim for 2mm slices.
Line a baking sheet with parchment paper, before placing the slices. Bake sourdough crackers for 50 minutes, flipping each after 25 minutes.
Let them cool on a cooling rack before serving. They'll get harder as they cool, so don’t worry if they’re still a bit soft when out of the oven.
Store sourdough crackers in an airtight container for up to 3 weeks.