Wash the mint leaves and raspberries carefully, dab them dry and put them in a drinking glass with a thick, stable base. Pour the lime juice, sugar syrup and Darbo raspberry fruit syrup over them. Use a pestle to thoroughly press the mint and raspberries. Fill the glass approximately two thirds full with crushed ice. Stir everything together thoroughly with a spoon. Pour the rum over the top, and top up the drink with soda water. Stir again briefly. Put the mint sprig into the glass and serve the drink immediately with a straw.