In a large saucepan, melt the butter over low heat, stirring gently. Once melted, add the marshmallows and stir until fully melted and smooth.

Remove from heat and pour in the Rice Crispy cereal. Fold the cereal into the melted marshmallow mixture until well coated.

Transfer the mixture into a greased 9x13 inch dish and press down firmly to compact the mixture.

In a small saucepan, combine the caramel candies and heavy cream. Cook over low heat, stirring until melted and smooth. Pour evenly over the Rice Crispy layer.

In a microwave-safe bowl, melt the chocolate chips in 20-second intervals, stirring until smooth. Pour evenly over the caramel layer and sprinkle sea salt if desired.

Allow the treats to cool completely at room temperature before slicing into squares.