In a medium saucepan, combine fresh blueberries, sugar, lemon juice, balsamic vinegar, and the split vanilla bean. Using a potato masher, gently crush the blueberries to release their juices. Cover the saucepan with a lid and refrigerate overnight.

The following day, remove the saucepan from the fridge and uncover it. Place the mixture over low heat and cook for about an hour, stirring occasionally.

On Day Three, increase the heat to medium and bring the blueberry vanilla mixture to a boil, stirring frequently to avoid burning. Boil until it reaches a temperature of 223°F (106°C).

Once the desired temperature is reached, remove the saucepan from heat. Discard the vanilla bean or add vanilla extract for added flavor. Ladle the hot jam into sterilized jars, sealing them tightly.