Step 1: Finely chop the white chocolate. In a heatproof bowl set over a saucepan of simmering water (double boiler method) or in a microwave-safe bowl, melt the white chocolate until smooth and creamy. If using a microwave, heat in 30-second intervals, stirring well after each, until fully melted. Stir in the optional butter and pinch of salt until combined.
Step 2: Remove the melted white chocolate from the heat. Gently fold in the finely chopped dried cranberries and chopped pistachios until evenly distributed.
Step 3: Cover the bowl with plastic wrap and refrigerate for 1 to 2 hours, or until the mixture is firm enough to roll. This is a crucial step for the truffles to hold their shape.
Step 4: Once chilled, scoop out small portions of the mixture (about 1 tablespoon each) and roll them between your palms to form smooth, uniform balls. Place the rolled truffles on a parchment-lined baking sheet.
Step 5: If desired, roll the truffles in additional finely chopped pistachios, powdered sugar, or cocoa powder for an enhanced visual appeal and texture.
Step 6: Return the coated truffles to the refrigerator for at least 30 minutes to set completely before serving. Store any leftover truffles in an airtight container in the refrigerator for up to 1 week.