Wash, peel, and core apples, then chop into evenly sized pieces and add to a slow cooker.
Add brown sugar, cinnamon sticks, ground cardamom, ground cloves, salt, freshly grated nutmeg, and 1 vanilla bean, slit down the middle.
Cover and cook for two hours on low. Stir after two hours and add ½ cup of water if the mixture is too dry.
Cook for two more hours, then remove the cinnamon stick and vanilla bean and blend with an immersion blender until smooth.
Continue cooking with the lid slightly ajar or completely off, stirring occasionally, until the apple butter is thick, dark, and spreadable. This can take up to 3 to 4 more hours.
Notes
See post for canning instructions.
If possible, use a mixture of apples. Combining sweet and tart varieties can give your homemade apple butter a more balanced flavor.
Adjust the sugar to taste. Apples vary in sweetness, so start with less sugar and add more after the apples have softened.
Don't rush the cooking process. Apple butter develops its rich flavor and dark color as it cooks down. Allow extra time for moisture to evaporate after blending.
For extra smooth apple butter, run the apple mixture through a food mill!
Once the apples are blended, uncover the slow cooker to help excess moisture to evaporate. Stir occasionally to prevent the mixture from sticking around the edges.
Check the consistency before calling it done. Apple butter should be thick and spreadable, not watery like applesauce. Remember that it will thicken a little more as it cools.