Spray a 9x9 pan with cooking spray and set aside.

In a large pot, melt butter, marshmallows, and salted caramel sauce over low heat, stirring occasionally. Once the mixture is melted, remove from heat and stir gently stir in the cereal.

Pour mixture into prepared pan and press in evenly. Sprinkle with sea salt or fleur de sel. Allow to cool completely before cutting into squares.

Note-you can use a 9x13 pan, but I like my Rice Krispies treats thicker. Spray your hands with cooking spray and press the treats into the pan, this will help the mixture from sticking to your hands.