Put the coffee grounds in a pan with 250ml water. Add the cardamom pods, lemon peel, cloves and cinnamon stick. Bring to the boil, then strain though a sieve lined with 2 pieces of kitchen paper. Leave to cool.
Pour 50ml of the coffee mixture into a cocktail shaker filled with ice then add the egg white, spiced rum and lemon juice. Shake hard for 1-2 mins then double strain into 2 coupe or martini glasses. Decorate with another cardamom pod and a few drops of Angostura bitters if you like.