Muddle the blackberries in a shaker.
Add ingredients into shaker.
Add ice cubes into shaker.
Shake very vigorously.
Remove shaker lid.
Remove ice cubes.
Pour shaker contents into a frozen couple glass.
I prefer to have the muddled blackberries in my glass, so I use ice cubes rather than crushed ice.
Flank speed rooster tails are quite an adventure.