Use a good dark chocolate, 60% cocoa or better; Hershey’s Special Dark will work, but Ghirardelli 60% Bittersweet Chocolate Chips or Baking Bar is better. For white bark, use Ghirardelli White Melting Wafers. Simply melt the chocolate (slowly!) and spread more or less evenly on a very well-oiled surface, ideally a baking pan with oiled parchment paper, though I knew a girl who used a greasy pizza stone in a pinch. Sprinkle with chopped pecans while still hot, and another sprinkling when still sticky. Cool and break into pieces.