Place the bittersweet chocolate and butter in a medium glass mixing bowl. Microwave for 30 seconds. Remove and stir, and repeat this process 1 more time. Set aside.
Heat the heavy cream and corn syrup in a small saucepan over medium heat until simmering. Remove from the heat and pour the mixture over the melted chocolate mixture; let stand for 2 minutes. Using a rubber spatula, stir gently, starting in the middle of the bowl and working in concentric circles until all chocolate is melted and the mixture is smooth and creamy. Gently stir in the brandy. Pour the mixture into an 8-by-8-inch glass baking dish and place in the refrigerator for 1 hour.
Using a melon baller, scoop the chocolate onto a half-sheet pan lined with parchment paper and return to the refrigerator for 30 minutes.
Place the cocoa powder, nuts, and/or toasted coconut each in its own pie pan and set aside.
In the meantime, place a heating pad in a large bowl and set the pad to medium. Place the 8 ounces of chocolate into a medium mixing bowl and set on top of the heating pad-lined bowl. Depending on the heating pad, you may need to adjust the heat up or down. Stirring the chocolate occasionally, test the temperature of the chocolate and continue heating until it reaches 90 to 92ºF; do not allow the chocolate to go above 94ºF. If you do, the coating will not have a nice snap to it when you bite into the chocolate. Once you have reached the optimal temperature, adjust the heat to maintain it.
Remove the truffles from the refrigerator and shape into balls by rolling between the palms of your hands. Use powder-free vinyl or latex gloves, if desired.
Dip an ice cream scoop into the chocolate and turn upside down to remove excess chocolate. Place truffles 1 at a time into the scoop and roll around until coated. Then, place the truffle into the dish with either the cocoa powder, nuts, or coconut. Move the truffle around to coat; leave truffle in the coating for 10 to 15 seconds before removing. In the meantime, continue placing the chocolate-coated truffles in the cocoa or other secondary coating. After 10 to 15 seconds, remove the truffle to a parchment-lined half-sheet pan. Repeat until all truffles are coated. Allow to set in a coo,l dry place for at least 1 hour, or store in an airtight container in the refrigerator. Truffles are best when served at room temperature.