Sprinkle gelatin over 1/4 cup of water, and let stand 2 min

In a saucepan heat over medium heat 1/2 cup buttermilk and 1/2 cup sugar until sugar dissolves sirring occasionally

Reduce heat to low and whisk in gelatin. Cook 1-2 min until gelatin dissolves

Remove from heat and stir in 2 1/4 cups buttermilk

Pour into 8 4 oz ramekins. Cover in plastic wrap and refrigerate at least 4 hrs until well chilled and set

Reserve 1/3 cup blackberries for garnish.

In blender puree remaining blackberries, lemon juice, 2 tbsp water, 4 tsp sugar

Pour puree through a sieve to remove seeds

Run a tip of a knife around edge of each ramekin to free the panna cotta and invert onto plates

Spoon sauce around panna cotta and garnish with remaining blackberries