Part 1: Making the Ganache

1. Prepare the Chocolate: Finely chop your chocolate bar and place it in a medium-sized, heat-proof bowl. The smaller and more uniform the pieces, the more evenly and quickly they will melt. If using pistoles, you can skip this step.
2. Heat the Cream: Pour the heavy cream into a small saucepan. Heat it over medium heat just until it begins to simmer gently around the edges. You’ll see small bubbles forming. Do not let it come to a rolling boil, as this can scorch the cream and cause the ganache to split or become oily.
3. Combine Cream and Chocolate: Immediately pour the hot cream over the chopped chocolate in the bowl. Gently nudge the chocolate to ensure it’s all submerged beneath the cream. Let the mixture sit undisturbed for 5 full minutes. This allows the heat from the cream to gently and evenly melt the chocolate without any agitation.
4. Emulsify the Ganache: After 5 minutes, add the room temperature butter pieces (if using), vanilla extract, and salt to the bowl. Begin to stir the mixture slowly and gently from the very center of the bowl, making small circles. As you stir, you will see the chocolate and cream start to come together in the middle, forming a glossy, thick emulsion. Gradually widen your circles, incorporating all the ingredients from the sides of the bowl until the ganache is completely smooth, dark, and glossy. Avoid whisking vigorously, as this can incorporate too much air.

Part 2: Chilling the Ganache

1. First Chill: Press a piece of plastic wrap directly onto the surface of the ganache to prevent a skin from forming.
2. Refrigerate: Place the bowl in the refrigerator for 1 to 2 hours, or until it is firm enough to scoop but not rock-hard. The texture should be similar to firm cookie dough. Chilling for too long will make it difficult to scoop. If this happens, let it sit at room temperature for 15-20 minutes to soften slightly.

Part 3: Shaping and Rolling the Truffles

1. Prepare Your Station: Line a baking sheet with parchment paper. Pour your cocoa powder into a shallow bowl or dish.
2. Scoop the Truffles: Using a small cookie scoop or two teaspoons, scoop out portions of the chilled ganache and drop them onto the prepared baking sheet. This ensures all your truffles are a uniform size. Work quickly, as the heat from your hands can start to melt the ganache.
3. Chill Again (Optional but Recommended): For cleaner rolling, place the baking sheet with the scooped ganache mounds back into the refrigerator for another 15-20 minutes to firm up again.
4. Roll and Dust: Lightly dust your hands with a bit of cocoa powder to prevent sticking. Take one ganache mound at a time and quickly roll it between your palms to form a rustic, slightly imperfect ball. Immediately drop the ball into the bowl of cocoa powder and roll it around to coat it completely.
5. Final Placement: Using a fork or your fingertips, lift the coated truffle from the cocoa powder, gently tapping off any excess, and place it back on the parchment-lined baking sheet.
6. Repeat: Continue this process with the remaining ganache.