Heat the butter and marshmallows in a large saucepan over medium heat.
Once melted remove from heat and stir in the Rice Krispies.
Press into a 13 x 9 baking dish coated with cooking spray. Allow to sit for 10-15 minutes.
Pour the Dulce de Leche into a microwave safe bowl and heat in the microwave for 30 seconds. Stir well and pour over top of the Rice Krispies Treats. Smooth in an even layer and let cool 5-10 minutes.
Put the chocolate in a microwave safe bowl and heat in 20 ssecond intervals in the microwave, stirring after each heating, until completely melted. Pour over top of the Dulce de Leche and gently smooth in an even layer.