Add all of the ingredients except the cloves and allspice to a crock pot. Stir well to combine. Cook on low for 4 hours, stirring several times to keep the mixture from sticking.
Add the cloves and allspice. Cool for 1-2 more hours or until thick (this time may vary based on your crock pot). Continue stirring to prevent sticking or burning. If at the end you want the pumpkin butter to be thicker, remove the lid and continue cooking until it reaches the desired consistency.
Transfer the pumpkin butter to jars and allow them to cool, then store them in the refrigerator or freezer. Pumpkin butter will keep for 2-3 weeks in the refrigerator or for up to a year in the freezer.