Preheat your oven to 350 degrees.
Line a rimmed 9x13 baking sheet with parchment paper, letting the parchment hang over the sides of the pan to form a sling.
In a large mixing bowl, combine the dry ingredients: Dates, oats, almonds, salt and cinnamon. Stir to evenly distribute.
In a medium mixing bowl, combine the wet ingredients: Peanut butter, discard, oil, honey and vanilla. Use a fork to make sure they are well combined.
Pour the wet ingredients over the dry ingredients. Use a spoon to mix them thoroughly.
Pour the mixture into the prepared pan. Use clean hands to press the mixture into all four corners of the pan and press down to get rid of any air pockets. This more pressed together the ingredients are, the better your sourdough granola bars will hold together.
Place the pan in the preheated oven and bake for 25-30 minutes, until the edges of the granola bars are starting to brown. Remove from the oven and allow to cool completely.
Once cool, remove the bars from the pan using your parchment sling. Use a sharp knife to cut the granola bars to your desired size. Store in an airtight container and enjoy!