I was at a Sri Lanken friend's house in the weekend and was lucky enough to sample a few of his father's curries. He was very cagey about what went in the curries and the finer details (secret family recipes etc!) and wouldn't tell me what one of the key ingredients was in a 'black pork curry', only that it was a sticky dark paste that you can only buy in Sri Lanka (said with a glint in his eye). I suspect it was tamarind - can anyone else shed any light on this? And does anyone know of any good Sri Lanken recipe books?