Preheat oven to 350 degrees F. Line an 8 inch square metal pan with foil and spray foil with cooking spray or just line it with nonstick foil.Melt the butter in a saucepan or microwave-safe dish, then remove from heat and let cool.Stir the flour, baking soda, salt and sugar together in the mixing bowl.
Whisk together the egg yolk, vanilla and melted butter, then pour into dry mixture and stir until crumbly. Put 1 cup of the mixture in the refrigerator (chilling it a bit helps make it easier to crumble). Press remaining into the pan.Unwrap the caramel circles and lay them over the dough.Crumble the reserved dough over the caramel and sprinkle chocolate chips or nuts on the top.
Bake on center rack for 20 to 23 minutes.
Let cool completely at room temperature. For a cleaner cut, chill for about an hour or until firm and cold.Lift from pan and cut into squares or bars
