Chop the chocolate into small pieces and put it into a medium-sized, heat-proof bowl.
Warm the cream over medium heat. As soon as it starts to simmer, remove it from the heat and pour it over the chocolate. DO NOT MIX. Let the cream and chocolate sit for 5 minutes.
After 5 minutes, add the vanilla (if using) and stir the chocolate.
Place the chocolate into the fridge and let it cool for at least 2 hours.
Once the chocolate is cool, use a small cookie scoop or tablespoon to scoop it into balls.
Place the toppings you choose into shallow bowls. Using your hands, roll the truffles into balls then roll the balls in the toppings so that they are well-coated. (See notes)
It's easiest (and the least messy) if you roll all the truffles into balls before you roll the balls in the toppings you choose. If you use nuts or sprinkles, roll each truffle a few times in your hand to soften the chocolate before rolling them in the nuts of sprinkles. It will help the toppings stick. This extra step isn't necessary if you use cocoa powder.