Recipe - Chocolate Caramel Shortbread Bars

This recipe comes from www.Annies-Eats.com.  Thank you, Annie!  Please visit her website to follow her adventures in the kitchen.
I've made these several times, to rave reviews.  You have to plan ahead, as each layer needs to cool before you add the next, but the time is well worth it!

Shortbread Layer:
1 c soft butter
1/2 c sugar
2 c flour
2 t baking powder
   Cream butter and sugar, then stir in flour and baking powder.
   Press into a well-greased 13x9 pan.
   Bake at 350 for about 16 minutes.  Let cool completely.

Caramel Layer:
1 c butter
1 c sugar
1/4 c light corn syrup
2 can sweetened condensed milk
   Combine in a saucepan over medium heat and cook until a deep caramel color.
   Stir continuously!!
   (a commenter on Annie's blog recommends cooking to soft ball stage)
   Pour over shortbread layer and chill thoroughly.

Chocolate Layer:
8 oz semi-sweet chocolate chips
1 T light corn syrup
1/2 c butter
   Combine in a double boiler over simmering water, stirring, until smooth.
   Pour over caramel and spread smooth.
   Let cool about 5 minutes.
flaked sea salt
   Sprinkle over chocolate layer and chill until ready to serve.
 
   Cut with a thin knife - dip in hot water between cuts.