Ganache can be flavored by simply adding ingredients to the chocolate/cream mixture or by infusing the cream first. Adding liqueur requires a small adjustment to recipes; see Boozy Chocolate Truffles.
Before proceeding with a truffle recipe, heat the cream or coconut milk to just under a simmer and add one of the following (halve the amounts for Milk or White Chocolate Truffles):
Cover, remove from the heat, and allow to steep for 30 minutes. Strain and reheat before adding to the chocolate.
Or, after combining the cream and chocolate, stir one of the following into the ganache while it is still warm: