1. Chop the dark chocolate and melt it in a heatproof bowl over simmering water or in short microwave bursts until smooth.

2. Heat the cream until just steaming, then whisk in the sourdough discard until fully combined.

3. Pour the warm sourdough cream mixture over the melted chocolate and let sit for 30 seconds, then stir until glossy and smooth.

4. Fold in the butter and sugar, if using, until the ganache is thick and luxurious.

5. Refrigerate the ganache for about 1 hour or until firm enough to scoop.

6. Using a small scoop or teaspoon, portion the chilled ganache into 1-inch rounds and roll between your palms to form smooth spheres.

7. Roll each truffle in cocoa powder or dip in melted chocolate for a glossy shell and place on a parchment-lined tray.

8. Chill the coated truffles for 15 minutes to set, then store in an airtight container in the refrigerator for up to 10 days or freeze for up to 2 months.

9. Allow frozen or refrigerated truffles to sit at room temperature for 10–15 minutes before serving.