Mix chocolate, banana, cream, and peanut butter together in a saucepan over medium heat; cook and stir mixture until melted (it may be partially lumpy due to peanut butter), 5 to 10 minutes. Pour mixture into a bowl and refrigerate until firm, 2 1/2 to 3 hours.
Scoop chocolate mixture with a melon baller and roll into 1-inch balls. Place confectioners' sugar in a shallow bowl; coat truffles with confectioners' sugar and refrigerate until firm, 1 to 2 more hours.