Combine 3 oz fresh or frozen blackberries, 0.5 oz simple syrup and 0.25 oz lime juice in a small blender or food processor. Pulse until smooth, about 10–15 seconds.

Strain the mixture through a fine-mesh sieve into a small bowl or jar, pressing with the back of a spoon to extract as much liquid as possible. Discard seeds and solids. Yield should be about 1 oz puree; refrigerate until ready to use.

Assemble Cocktail

Muddle

In a Moscow mule mug or a Collins/highball glass, add 3 fresh blackberries and gently muddle with the 0.5 oz fresh lime juice to release juices and aromatics. (If you made fresh blackberry puree, skip the muddling and proceed to the next step.)

Build

Fill the mug or glass with ice (about 1 cup). Add 2 oz vodka and 1 oz blackberry puree (or the strained blended blackberry mixture).

Top

Carefully top with 4 oz ginger beer. Stir gently twice with a bar spoon to integrate the puree without flattening the ginger beer.

Taste & adjust

Taste quickly. If the cocktail needs more brightness, add another 0.25 oz fresh lime juice. If it needs sweetness, add 0.25 oz simple syrup and stir gently.

Garnish & serve

Garnish with a lime wheel or wedge, a mint sprig (optional), and one or two whole blackberries on a cocktail pick. Serve immediately with a straw.