- 5 pints of blueberries
- 4 large plums
- 2 cups organic golden cane sugar
- zest and juice of one organic lemon
- Spread blueberries on a tray or baking sheet and check over quickly for large stems, leaves or bugs.
- Wash blueberries and plums and drain well. Cut plums in half and remove pit.
- Combine fruit in a food processor and blend until it is a smooth puree. You should have about 8 cups of puree.
- Add puree to a slow-cooker, cover and turn to high. After one hour (set a timer!), stir the butter and leave the lid open a crack for the remainder of the cooking time. This will allow for the steam to escape and the butter to reduce and thicken.
- Cook the butter for 4-5 hours on high or 6-8 on low. Times WILL vary with different slow-cooker brands. Be sure to stir the fruit butter once an hour or so.
- In the final hour of cooking, add the sugar, lemon zest, and lemon juice. Stir well, and bring to prepare your jars and water bath for canning.
- Fill a canning pot with 6 half-pint jars or 3-pint jars. Bring to a boil and boil for 10 minutes to sterilize the jars.
- Place rings and lids in a small sauce pot, cover with water, and bring to a simmer.
- Once blueberry butter is the consistency of ketchup, it is ready to can.If you want it super smooth, like baby food, you can puree it again with an immersion blender. If not, your butter is ready to can.
- Working with one jar at a time, remove jars from canner and fill with butter. Wipe the rims with a clean cloth, place a lid and a ring on the top, and return to the canner.
- Bring canner back up to a boil and process jars for 10 minutes. Carefully remove jars and allow to cool on the counter overnight.
- Check that all the jars have sealed, then store in a cool place for up to 6 months.
~You can use a blender, Vitamix, or food processor to puree your blueberries. ~I used organic golden cane sugar for this recipe, but white sugar can certainly be substituted. And I'd love to try it with maple syrup. ~Slow-cookers may vary. Marisa recommends cooking the butter for up to 8 hours on low, but I had mine on high the whole time (5 hours) and had no scorching.
** Note from Chella The processing time listed is for altitudes of 1,000 feet or less. For altitudes up to 3,000 feet, add 5 minutes; 6,000 feet, add 10 minutes; 8,000 feet, add 15 minutes; 10,000 feet, add 20 minutes.**