Chop chocolate finely so it will melt more quickly and evenly. If using coconut milk, be sure it’s the full-fat canned type. Heat the milk or cream just until it barely begins to boil. Pour over the chocolate, add the salt and vanilla if using, and stir until smooth. Refrigerate at least 2 hours, or until firm enough to scoop out and roll balls with your hands or a mini cookie scoop. If desired, roll truffles in cocoa powder, sprinkles, crushed walnuts or almonds, coconut, powdered sugar, or melted chocolate. Set on a parchment-lined plate, and refrigerate or freeze until ready to serve. Leftover truffles can be refrigerated for 1-2 months.