Pour the cream into a small pan and bring to the boil. Take the pan off the heat and break in 200 g (7 oz) plain dark chocolate. Leave to stand until it has melted, then stir in the brandy or rum and mix until smooth. Chill for 4 hours until the truffle mixture is firm.
Line a baking sheet with waxed paper and dust with cocoa powder. Scoop a little truffle mixture on to a teaspoon, then transfer it to a second spoon and back to the first again, making a well-rounded egg shape (or use a melon baller). Slide the truffle on to the cocoa-dusted paper. Repeat until all the mixture is used up. Chill again for 2 hours, or overnight if possible, until firm.
Melt 200 g (7 oz) plain dark chocolate in a bowl over a pan of simmering water (see
Chill for at least 1 hour, then pack into petit-four cases and arrange in a gift box lined with purple tissue paper.