Melt the chocolate, cream and butter in a heatproof bowl over a small pan of just simmering water, or in the microwave in short blasts, stirring regularly. Stir in any flavourings you like (add them gradually and taste the mix, the flavour will be stronger when chilled). Transfer to a small baking dish or shallow container and chill until set, about 4 hrs or overnight.
Using a large melon baller or a heaped teaspoon, scoop truffles from the set mixture, or using clean hands briefly roll between your palms, then transfer to a lined baking tray. Chill in the freezer for 30 mins to firm up.
To decorate, melt the chocolate the same way as in step 1, leave to cool a little, then drop the chilled truffles into the chocolate and lift out with a fork. Put back on a lined baking tray and sprinkle over any toppings, if using, and chill again in the fridge for 1-2 hrs, or freeze for 30 mins if you’re in a rush, until set. Store in a cool place or in the fridge until giving as a present or eating.