Melt butter in a saucepan over medium heat. Mix in 4 cups of marshmallows and melt completely. Add in Rice Krispies and the other 2 cups of marshmallows. Mix until the 2 cups of marshmallows are melted slightly.
Pour into sprayed pan and press Rice Krispies down evenly with silicon spatula.
In a small, microwavable bowl, melt together caramels and heavy cream in 30-second increments. (It took us about 1 min 15 seconds total)
Cut Rice Krispies into squares, place on parchment paper, and drizzle with melted caramel. If the caramel starts to set in the bowl before you can use it all up, place it in the microwave for a few more seconds to warm up!
After caramel is drizzled onto squares, sprinkle with course salt.
**If you’d rather drizzle the caramel on the Rice Krispies while they’re in the pan, you can do so. Cut the squares prior to drizzling and let the caramel sit for a minute before enjoying!