Finely chop 8 ounces of the chocolate and put in a bowl.
Combine the orange zest and the heavy cream in a small saucepan and bring to a boil. Strain the orange infused cream over the chocolate and let it set for one minute. Stir gently with a whisk (do not beat or you’ll incorporate air), starting in the center and working your way to the edge, until the ganache is smooth. Stir in the liqueur if using.Cover the bowl with a plastic wrap and let set at room temperature until thick enough to hold its shape, approximately 2 hours.Using a pastry bag with a 3/8-inch opening tip OR using a small cookie scoop (in which case the truffles will be much larger), pipe or scoop mounds (about 3/4 inch high and 3/4 inch wide if piping) on parchment-lined baking sheets.Refrigerate until firm, about 15 minutes.Meanwhile, melt the remaining 3 ounces of chocolate. With gloves on, coat the palm of your hands with melted chocolate and gently coat each chilled truffle. Immediately toss the coated truffles in chocolate powder with a fork.Store the truffles inside an airtight box at room temperature.
