If you use unsweetened baking chocolate, which has no sugar added, boil 1/4 cup honey with the cream. // In the restaurant, we always rolled our truffles, but at home, I'm usually too lazy to take the time to roll them, so I just chop the firm chocolate mixture into chunks and serve them that way. Piled on a serving plate, they're just as pretty - and definitely more inviting - than perfectly shaped balls, in my opinion.
Line a square baking pan or loaf pan with parchment paper, allowing plenty of paper to overlap the edges and tucking the paper into the corners as much as possible. Set aside.
Place chocolate, salt, and spices in a heat-proof bowl.
Place cream over medium-high heat in a heavy-bottomed saucepan and bring just to a boil.
Meanwhile, set a fine-mesh strainer over the bowl with the chocolate, then pour the boiled cream over chocolate, straining the milk as you pour.
Using a wooden spoon, stir quickly in small circles in the center of the bowl. The chocolate center will become a smooth, velvety emulsion. Gradually stir in larger circles, bringing in more chocolate from the sides. Keep enlarging the shiny center until all the chocolate is melted and completely smooth.
When the chocolate has cooled to room temperature and thickened noticeably, stir in the butter until smooth. Taste the chocolate and adjust spices as desired. Stir in vanilla extract.
Pour into the prepared pan and set in the refrigerator until the mixture is firm, 2-6 hours. Meanwhile, place cocoa powder in a bowl or pie plate and have at the ready.
Lift the chocolate block out of the pan, then using a sharp knife, chop the truffle mix into bite-size chunks. They need not be square. Drop each piece into the cocoa powder and dredge well. Shake off the excess cocoa and place pieces on a parchment-lined baking sheet or airtight storage container. Chill until ready to serve. Dust with chili powder just before serving, if desired.
Store in the refrigerator for up to 1 month, but let sit at room temperature for 20-30 minutes before serving.