(Makes one 10 x 15-inch baking pan or two pans of equivalent size)  
40 saltine crackers (1 sleeve) (or substitute graham crackers, we did)  
1 cup butter  
1 cup brown sugar  
2 cups (500ml) semisweet chocolate chips  
 3/4 cup (175ml) chopped nuts  
  Line a 10 x15-inch baking pan (or a couple of smaller pans), with aluminum foil so the foil
  extends up the sides of the pan slightly  
  Cover bottom of the pan (s) with 5 rows of  8 saltine crackers, (or equivalent other crackers)
  In a medium saucepan, melt butter  
  Add brown sugar, bring to a boil, boil for 3 minutes without stirring.  
  Carefully pour hot liquid over crackers.  
  Bake in a preheated 400F oven for 5 minutes.  
  Carefully remove pan from oven.  
  If crackers have shifted a little, use a fork to quickly push them back into position.
  Sprinkle with chocolate chips.  
  Let stand for 1 minute, then gently spread melted chips with spatula or back of spoon.
  Sprinle nuts over chocolate and press down lightly.  
  Let stand or chill until firm.  
  Lift whole slab out of pan, turn over and break into pieces with a table knife handle or
  similar weighted object.  
  Store in refrigerator.  
  Can be frozen.  
  Optional: Any kind of nuts can be used, we used walnut pieces.  
  Use mini marshmallows instead of nuts, (or some of each at opposite ends of pan)
  After sprinkling marshmallows, pop the pan into the oven briefly to soften marshmallows