When ready to dip the truffles, melt the chocolate in a heatproof bowl set over a pot of simmering water. You can also melt them in the microwave, heating in 30 second intervals stirring in between. If you need it thinner, add a bit of oil or butter. Dip each chilled truffle, one at a time using a fork, coating in chocolate and shaking gently or tapping against the bowl to remove the excess. Transfer to a wax-paper lined surface. If using mini chocolate chips for garnish, sprinkle on top quickly after dipping each truffle before the chocolate sets.