Christmas Crack

1 sleeve of saltine crackers ( I used Town House)
3/4 cup unsalted butter
1/2 cup brown sugar, packed
1/2 tsp. baking soda
12 oz. bag of semi sweet or milk chocolate chips ( I used milk) 
topping of your choice ( I've used various nuts in the past, this year I opted for Christmas nonpareils) 

Preheat oven to 375 degrees F.  Completely line a 15 1/2" x 10 1/2" x 1" cookie sheet with nonstick foil.  ( Pan size is important, if you go too big, like a half sheet size, there won't be enough toffee mixture to completely cover the crackers.  If you go too small, you might have a bubble over in the oven)  

Lay crackers on the bottom of the lined sheet pan, with sides touching in one big rectangle.  The square might not quite be big enough to cover the entire cookie sheet.  

In a med sauce pan, melt the butter with the sugar.  Stir to dissolve the sugar.  Bring to boil.  Remove from heat and add in the baking soda.  Mixture may become frothy.  Carefully pour the hot mixture over the crackers.  Spread around to cover the crackers as best you can.  Pop  the sheet into the oven for 8 minutes.  It will bubble up in the oven.  

Remove from oven, and sprinkle chocolate chips on top.  Return to oven for 2 minutes.  Smooth chocolate over the surface of the crackers using a spatula.  Top with sprinkles or nuts.  Allow to harden and cut into small squares.  Store in airtight container.