Heat the cream. Add the vanilla sugar and coffee powder and stir to dissolve. Chop the milk chocolate coating. Chop the dark chocolate, set 300 grams (approximately 10.5 oz) each aside. Melt the remaining 100 grams (approximately 3.5 oz) of milk chocolate coating with the coffee-cream, stirring constantly. Let cool until the mixture begins to thicken (it should not be completely cooled). Beat the mixture with a mixer, and gradually add the butter and the orange liqueur.
Spoon the cream into a piping bag with fitted with a plain tip and pipe into the hollow chocolate balls (they should be completely full). Chill overnight to set.
Melt the reserved dark chocolate over a hot water bath and maintain a constant temperature of about 28°C (approximately 75°F). Place some chocolate in your palms and roll the filled hollow balls between you hands. place on wax paper. Then dip the prepared truffles with a chocolate dipping fork into the chocolate coating and place on a lattice rack. Let the chocolate coating set briefly, then roll the truffle chocolates with the fork on the grid to shape. Place the set chocolate truffles in foil or parchment paper.