Add all of the ingredients to the crockpot.
Cover and cook for 2-3 hours on low. Stir a couple of times while it’s cooking.
Remove the cinnamon stick (if using), and puree the hot blueberry butter using a hand blender. Add the cinnamon stick back in.
Offset the lid and continue cooking for another 6-8 hours. Once per hour, stir the mixture.
Transfer the blueberry butter once it’s thick to sterile canning jars and seal with the metal lid.
Allow it to cool to room temperature before storing or serving