Place the dark chocolate in a microwave-safe bowl and melt in 30-second bursts, stirring well between each, until smooth and glossy. The chocolate should be around 40°C (104°F).
In a separate mixing bowl, combine the peanut butter, crushed cookies, and powdered sugar. Mix everything together with a spatula until the mixture is thick, sticky, and well incorporated—this is your truffle filling.
Using your hands, roll the mixture into 1-inch balls and place them on the parchment-lined baking sheet. The balls should feel firm yet pliable.
Chill the formed balls in the refrigerator for about 30 minutes until they are firm and easy to handle.
Once chilled, use a fork to dip each ball into the melted chocolate, turning to coat evenly. Gently tap the fork against the side of the bowl to remove excess chocolate.
Place each coated truffle back on the parchment-lined sheet and, if desired, drizzle extra melted chocolate over the top for decoration.
Allow the chocolate coating to set at room temperature or refrigerate for about 15 minutes until firm and shiny.
Optionally, dust with cocoa powder for an elegant finish, then serve these decadent bites chilled or at room temperature.