Ingredients:

  • 6 cups (900g) fresh blackberries, rinsed and patted dry
  • 2 cups (400g) granulated sugar
  • 1 tbsp (15ml) lemon juice, freshly squeezed
  • 1/2 cup (64g) cornstarch
  • 1/4 cup (60ml) cold water
  • 1 tsp (5g) ground cinnamon
  • 1/4 tsp (1.5g) salt
  • 1 tsp (5ml) vanilla extract

Instructions:

  1. Combine the blackberries, sugar, lemon juice, cinnamon, and salt in a large heavy-bottomed pot. Heat over medium-low, stirring gently with a spatula to avoid crushing every berry. Simmer for 10–15 minutes until the berries release their juices and the mixture becomes fragrant.
  2. In a small bowl, whisk the cornstarch and cold water until completely smooth to create a slurry.
  3. Slowly drizzle the cornstarch slurry into the simmering berries while whisking constantly. Increase heat to medium-high and bring to a full rolling boil for exactly 1 minute until the filling is a heavy, glossy syrup. Remove from heat and stir in the vanilla extract.
  4. Ladle the hot filling into sterilized pint jars, leaving 1/4 inch of headspace. Wipe the rims clean, apply lids, and tighten bands to fingertip-tight.
  5. Process the jars in a boiling water bath for 10 minutes. Remove and let sit undisturbed for 24 hours to ensure a proper vacuum seal.