1. Melt the chocolate and butter in a bowl over a saucepan of hot water.
2. Remove from the heat and stir in remaining ingredients except the chocolate vermicelli.
3. Chill in the refrigerator until firm enough to handle.
4. Mould into balls the size of a small walnut and roll in the vermicelli.
5. Leave to set on greaseproof paper before putting in individual paper cases.