Using a food processor, pulse chopped chocolate until it is finely chopped. If doing by hand, use a large knife and chop chocolate very fine.

In a small, heavy saucepan, heat the cream until hot and bubbles form around the edges. Remove from heat and allow to sit for a minute. Add chocolate all at once, shaking the pan so that the chocolate sinks into the cream. When the pieces are soft, stir with a rubber spatula until the ganache is smooth and thoroughly blended. Add vanilla and stir to incorporate.

Pour into bowl. Loosely cover the mixture and refrigerate, stirring occasionally until the ganache holds its shape, 30 minutes to 1 hour.

Line a baking sheet with parchment or waxed paper. Anchor the sheet with a damp towel or tape. Using a melon baller or pastry bag, create truffles that are about 3/4 of an inch in diameter. Refrigerate until firm, about 30 minutes.

Roll each chocolate truffle gently in your hands, then roll in cocoa powder, nuts, coconut, etc. until covered. Store in an airtight container in the refrigerator for up to one month.