Heath Bar Toffee Bark

I love old fashioned desserts such as traditional toffee bark.  It's one of my favorite classic holiday desserts.  I also enjoy the modern "Christmas cracker" toffee dessert that my sister-in-law brings to family gatherings.  I decided to combine the traditional dessert with the modern salty version with this Heath Bar toffee bark.  I love both versions, so this is bound to be twice as delicious! 
Ingredients
1 cup light brown sugar; 1 cup Land O' Lakes butter with canola oil (try to use this brand as possible; it melts easily but isn't too greasy); 1/4 tsp. sea salt; 2 cups semi-sweet chocolate chips; 2 tablespoons shortening; 2 full size Heath Bars
Directions
In a medium saucepan, melt the butter, sea salt, and brown sugar on stove top over medium heat.  Turn heat up slightly above medium and bring to a full boil.  Immediately turn heat back to medium.  Boil for four minutes, stirring every 30 seconds.  Do not over stir, so margarine and sugar do not separate.  Mixture should be a dark amber color when ready. Pour onto an 8x8 or HALF of a rectangular 9X13 baking sheet fitted with parchment paper.  Use a spatula to spread.  Place the chocolate chips and shortening in small microwave safe bowl.  Heat for 30 seconds.  Stir.  Repeat until fully melted.  Use a spatula to spread the melted chocolate over the toffee layer.  Crush the Heath Bar into bite size pieces.  Garnish over the top of the chocolate.  Place toffee bark in the refrigerator for 1 hour to harden.  Break into pieces to serve.  Serve immediately.  Store remaining bark in a storage container in the refrigerator so toffee does not soften.