Preheat oven to 325°
Beat butter and both sugars.
Add the vanilla.
Add the flour.
Line an 8 x 8 inch pan with non-stick foil.
Press one-third of the dough into the bottom of the pan and bake 20 mins.
Meanwhile chill the rest of the dough.
Spread the dulce de leche or caramel sauce over the crust carefully.
Crumble the rest of the dough on top of the dulce/caramel.
Bake about 30 minutes more until lightly golden.
Cool and cut into bars.