Add the blackberries to your cocktail shaker and use your muddler to mash them up to get the juices out.
Add your lime juice, Italicus liqueur and gin to the cocktail shaker.
Fill the shaker with ice, seal it up and give it 15-20 hard shakes.
Strain the drink into your cocktail glass. (I recommend double straining, where you use a fine mesh strainer in addition to the regular strainer, just to catch any blackberry seeds.)
Add a blackberry and some fresh mint to a cocktail pick, and rest it on the side of the glass as a garnish before serving. Cheers!
Notes
If you'd like to make this cocktail sweeter, you can use a lime cordial like Rose's Lime instead of fresh lime juice. Or, just add up to ½ ounce (15 ml) of simple syrup.
You can easily make this drink into a highball by serving it over ice and topping it off with seltzer.
If you don't have fresh mint, a slice of lime makes a great garnish too.
If you don't have Italicus, try using Fabbri bergamot syrup.