Put the chocolate and heavy cream in a small bowl set over--not in!--simmering water, and stir until the chocolate melts. Remove from the heat and let cool for 5 minutes.
Put half of the melted chocolate mixture into a blender along with the bananas, yogurt, milk and peanut butter. Blend until smooth and frothy, about 2 minutes.
Drizzle the remaining melted chocolate in the bottom and down the sides of two large glasses. Fill each glass with the smoothie and serve immediately.
Recipe courtesy of Bobby Flay