Add all ingredients into bowl and toss to combine. Refrigerate overnight to allow flavors to blend.
Place the mixture into the pressure cooker insert and place the insert into the pressure cooker.
Keeping the lid off, set to Sauté and bring to a boil, stirring often. Boil for 5 minutes. Use a potato masher and smash the blackberry mixture.
Place the lid on pressure cooker and set to manual for 8 minutes. Allow natural release. Remove the lid and set back to sauté setting.
Bring jam to a boil while stirring constantly and boil for 5 minutes. Remove from heat and allow to cool. Ladle the jam into jars and refrigerate.