Place the chocolate squares in a small, heatproof bowl with the crushed cardamom, coffee liqueur and olive oil and set over a pan of barely simmering water. Leave the chocolate to melt very slowly without stirring for about 8 minutes.
Remove the bowl of chocolate from the heat and quickly beat in the egg yolks. Set aside while you put the egg whites in a large bowl and whisk until stiff. Stir 1 tablespoon of the beaten whites into the chocolate mixture to slacken it, then carefully fold in the remaining egg whites with a metal spoon.
Divide the mixture between 4 ramekins or pretty coffee cups. Cover and chill for 2 hours, or until required. Serve with a little whipped cream and a dusting of cocoa powder.