Add the sugar and water to a medium saucepan and heat over medium heat until the sugar dissolves. Continue to heat for 5-10 minutes, until the syrup thickens slightly. Turn off the heat and allow to cool. Transfer to a jar or bottle and store in the fridge.

Chill the cocktail glasses by filling with ice while you make the cocktail.

Squeeze the juice from the lime and add to your cocktail shaker - it doesn't matter if the juice and pulp make it into the mixture and the whole thing will be strained later.

Measure in the rum and sugar syrup.

Lay the mint leaves on one hand and slap them very hard with the other hand to release their essential oils. Add to the shaker.

Thoroughly crush and combine the ingredients with a cocktail muddler, turning the shaker as you go to ensure the mixture is evenly muddled. If you don't have one, use some kind of similar implement and do your best!

Fill the shaker three quarters full with ice. Put the lid on your shaker and shake hard back and forth, while moving it through the air in a clockwise/pentagonal shape so the liquid rotates as well as moving up and down. When the shaker is very cold and frosted it is ready.

Tip the ice out of the glasses and divide the rum mixture between the glasses. Top up with the chilled cava.

Pick a couple of the best looking mint leaves, lay flat on one of your palms and slap them hard with the other palm. Lay one leaf on the surface of each drink to garnish.

Drink!