Chop the dark chocolate into small pieces and microwave in a microwave-safe bowl in 30-second bursts, stirring each time until smooth and glossy. Set aside to cool slightly.
In a mixing bowl, combine the softened unsalted butter and peanut butter. Microwave for 20 seconds if needed to soften further, then stir until smooth and creamy.
Add the sifted powdered sugar and a pinch of salt to the peanut butter mixture. Stir well until the mixture is thick, smooth, and slightly sticky.
Pour the slightly cooled melted chocolate into the peanut butter mixture. Fold gently with a spatula until fully incorporated and glossy.
Cover the bowl and chill the mixture in the refrigerator for 30-45 minutes until it firms up enough to scoop.
Use a small cookie scoop to portion out the chilled mixture into small balls, about 1 inch in diameter. Roll each between your palms to smooth and place on a parchment-lined baking sheet.
Refrigerate the shaped truffles for another 15-20 minutes until they are firm and well set.
Re-melt the remaining dark chocolate briefly if needed. Using a fork, dip each truffle into the melted chocolate, turning to coat evenly, then gently tap off excess chocolate.
Place the coated truffles back on the parchment-lined sheet and refrigerate for 10 minutes until the chocolate coating is glossy and firm.
If desired, sift cocoa powder over the truffles for an elegant dusting. Let sit at room temperature for 5 minutes before serving.
