Ingredients 5 cups crushed blackberries (do not puree, crush with a potato masher) 7 cups sugar 1 (1 3/4 ounce) package dry pectin...

5 cups fresh or defrosted frozen blackberries 3/4 cup plus 1 Tbsp sugar 1 Tbsp cornstarch 1/8 tsp salt 1 Tbsp unsalted butter, cut into...