Use a really good vanilla-bean ice-cream - I prefer gelato - or play with different flavours (hazelnut, almond, coffee, or chocolate) and different liqueurs, from Nocello and Sambuca to aged dark rum.
1 or 2 scoops of chocolate gelato
1 double espresso
1 tbsp Frangelico, Nocello or similar
Grated dark chocolate
Place one or two scoops of gelato in each coffee cup.
Spoon the espresso coffee and liqueur over the top, scatter with grated chocolate and serve immediately.
Experiment to get the right ratio of ice-cream to cup size, and to strike the right balance between hot and cold, bitter and sweet. The gelato's sweet richness should be balanced by the strength of the coffee and the kick of the booze.