Preheat oven to 350. Cream butter,sugar,egg yolks,vanilla. Stir in flour and salt until well blended. Pat into a 13x10 rectangle on a greased baking sheet leaving one inch around baking sheet. Bake 20-25 minutes until nicely browned-it will be soft.
Remove from oven and immediately place separated squares of chocolate bars on top. Let stand until soft and spread over surface. Sprinkle with nuts and cut in small squares while still warm.