Chop the chocolate: Use a chef's knife to chop the chocolate as finely as possible; this will help it melt quickly and evenly. Then place it in a medium glass bowl. (Glass retains heat, so the chocolate will stay melted longer.)
Make the ganache: Heat the cream in a small saucepan over medium heat until bubbles form around the edge. Remove from the heat and add about one-fourth of the chocolate; whisk until smooth. Slowly pour the cream mixture over the remaining chocolate in the bowl and let sit until the chocolate melts, about 30 seconds. Puree the melted chocolate with an immersion blender or beat with a whisk until all the lumps disappear and the ganache is smooth. Stir in the butter until smooth, then add liqueur, if desired. (Jacques adds the liqueur last, so the flavor doesn't cook off.)
Pour and set: Line a rimmed baking sheet with plastic wrap, leaving a 2-foot overhang on one side. Pour the ganache onto the baking sheet and spread evenly with a rubber spatula. Fold the plastic wrap back over and press directly onto the surface of the ganache. Let cool at room temperature at least 4 hours or overnight.
For the truffles: Using two teaspoons, scoop small mounds of the ganache onto parchment-lined baking sheets. Set aside until firm enough to roll, about 15 minutes in the refrigerator or 2 hours at room temperature.
Roll into balls: Place the chocolate mounds between both palms, squeeze slightly and roll. Refrigerate until ready to coat.
Temper the chocolate: This is a gentle melting and cooling process that gives chocolate a glossy finish. For the coating, place the chopped chocolate in a heatproof bowl set over a saucepan of barely simmering water and stir until melted, about 40 minutes. Pour into a clean glass bowl; stir to cool to between 88 degrees and 90 degrees, about 40 minutes. (Jacques recommends a laser thermometer for checking the temperature.)
Dip and coat: Spread out the cocoa powder, coconut and nuts on parchment paper. One at a time, dip each truffle in the tempered chocolate with a two-prong dipping fork (you can buy one at a baking-supply store or break off the middle tines of a plastic fork). Lift the truffle and let the excess chocolate drip off. Roll in toppings and place on a rack to dry. Store in an airtight container for up to 2 weeks.