Prepare the Blackberries:

In the cocktail shaker, muddle the blackberries with the sugar (if you’re using it) until you’ve broken them down into a juicy pulp. This releases their color and flavor, enhancing the drink.

Mix the Drink:

Squeeze the juice from half of the lime into the shaker.

Add the vodka and a handful of ice.

Shake well to mix all the ingredients thoroughly.

Assemble the Drink:

Fill a highball glass with ice cubes.

Strain the mixture from the shaker over the ice in the glass, ensuring the seeds and the pulp are left behind.

Top up the glass with tonic water. Adjust the amount of tonic based on how strong or light you prefer your drink.

Garnish and Serve:

Slice the remaining half of the lime into rounds or wedges.

Garnish the drink with lime slices and a sprig of mint if desired.

Give the drink a gentle stir before serving.