This also comes from the book "Perfect Preserves" by M. Dalton King. One of my friends made it. It's very good!
- Pick over blueberries, removing all stems, leaves and damaged or unfit berries. Wash and place in a preserving pan with the lemon juice (and whole allspice, if using).
- Cook over medium heat until berries begin to soften (3--5 minutes). Add sugar and bring to a boil. Cook for 10 minutes, stirring often.
- Mix in the cassis and allspice (if using ground). Cook for 5 more minutes, until preserve is thickened and reaches 221°F.
- Ladle preserve into hot sterilized jars, leaving 1/2 inch headroom. Wipe rims clean and seal.
- Process 5 minutes in a boiling water bath. Cool, check seals, and alabel. Store for up to 1 year in a cool dark place.