Place the chocolate in a heat-proof bowl. Set aside.
Heat the heavy cream until it is simmering. You can heat it on the stove or in the microwave.
Add the butter to the chocolate and pour the heavy cream evenly on top. Cover and let the warm cream and chocolate sit for 5 minutes. Add the vanilla extract (or other flavoring) and stir until the chocolate has completely melted. Place a piece of plastic wrap directly on the surface (to avoid condensation) and refrigerate for 1-2 hours. Tip: Pour into a flat shallow dish, such as an 8- x 8-inch baking pan, so the mixture sets quickly and evenly. Scoop the set truffle mixture into 2 tsp-sized mounds. For larger truffles, use 1-Tbsp sized mounds (I used this cookie scoop to help me). Roll each into balls (if mixture is too sticky, see Troubleshooting Tips below).
Roll each ball into toppings as desired.
Cover tightly and store truffles at room temperature for 3-4 days or in the refrigerator for up to 2 weeks. Truffles taste best at room temperature.