Preparation

• Stir the cream, milk, and sugar in a 3-quart saucepan over medium heat until the sugar dissolves. Continue heating, undisturbed, until steam begins rising from the surface, about 2 minutes. Transfer to a blender. Add the blackberries, jam, vanilla, and salt and blend until smooth, about 1 minute. Strain through a fine-mesh sieve into a medium bowl. Refrigerate until thoroughly chilled, at least 6 hours or up to 1 day, covering with plastic wrap once cool.
• Stir the blackberry mixture and churn it in an ice cream machine according to the manufacturer’s instructions until it’s the consistency of soft serve ice cream. Serve or pack into a container, seal, and store in the freezer for up to 1 week.