Groovy
Kaffir lime leaf
SHAKE all ingredients with ice and fine strain into chilled glass.

Special ingredient #1: Kaffir lime syrup (Bring 250 ml water with 500g of sugar to the boil, pour into a blender with 30g of kaffir lime leaves. Beat well and strain through a coffee filter. Chill before use.)
[['6 cl', 'Bacardi 4 year old gold rum'], ['3 cl', 'Lime juice (freshly squeezed)'], ['1.5 cl', '*Special ingredient #1 (see above)'], ['2 dash', "Peychaud's or other Creole-style bitters"]]
[['6 cl', 'amber rum'], ['3 cl', 'lime juice'], ['1.5 cl', '*special ingredient #1'], ['2 dash', "peychaud's bitter"]]