• Combine blackberries, sugar, and lemon juice in a bowl. Stir to mix and dissolve sugar, mashing the berries a bit as your stir.
• Pour the berries and any accumulated juices into a saucepan. Stir in the basil. Bring to a boil over medium-high heat, stirring constantly. Use your spoon or a potato masher to break down the blackberries.
• Cook the jam until reduced and thickened, about 20 minutes. If the jam is splattering too much as you cook, reduce heat to medium. The jam is ready when it does not immediately pool back into the space after running a spoon through.
• Remove from heat and pour into jars. Let the jars cool to room temperature, then store in the refrigerator.

To water bath can

• If you want to water bath can this jam, bring a large pot of water to a boil before making the jam. Sterilize jars and set aside. Cook jam.
• Pour jam into jars, leaving ½-inch headspace. Apply lids and rings, then transfer jars to boiling water bath with a jar lifter. Process for 10 minutes, then turn off heat and let jars rest for 5 minutes. Remove to a towel-lined counter and let jars sit for 24 hours before checking for seals, labeling, and storing. Any unsealed jars must be stored in the refrigerator.