In the container of a blender, process blackberries until puréed. Strain through a fine-mesh sieve into a medium bowl, discarding seeds. Place 1⅔ cups (400 grams) blackberry juice in a medium Dutch oven. Add blueberries, sugar, almond liqueur, and vanilla bean and reserved seeds, stirring to combine. Let stand for 30 minutes.

Bring berry mixture to a boil over medium heat. Cook, stirring frequently, until mixture is thickened and jam leaves a trace when a spoon is dragged across bottom of pot, 20 to 25 minutes. Remove from heat, and let cool for 1 hour. Transfer jam to a clean jar. Jam will keep refrigerated for up to 2 weeks.