Set aside 36 macadamia nuts for garnish. Finely chop the remaining nuts; set aside.
In a small bowl, combine the peanut butter, confectioners' sugar, sour cream, vanilla and reserved chopped nuts. Cover and refrigerate for 15 minutes.
Meanwhile, in a microwave, melt chocolate; stir until smooth. Pipe about 1 teaspoon chocolate into each of 36 foil-lined miniature muffin cups. Chill for 10 minutes or until firm.
Spoon 1/2 teaspoon peanut butter mixture into each cup. Pipe enough additional chocolate into each cup to cover peanut butter filling. Top each with a macadamia nut. Chill for 10 minutes or until firm. Store in an airtight container in the refrigerator.