01 -
Line a 9x13 inch baking pan with parchment paper, leaving overhang on the sides for easy removal. Spray lightly with cooking spray.
02 -
In a medium saucepan over medium heat, melt the sugar, stirring constantly with a heat-resistant spatula or wooden spoon. The sugar will form clumps and eventually melt into a amber-colored liquid. Once completely melted, immediately add the butter. The mixture will bubble rapidly. Stir until the butter is completely melted, about 2-3 minutes.
03 -
Very slowly, drizzle in the heavy cream while stirring. The mixture will bubble rapidly again. Allow the mixture to boil for 1 minute. Remove from heat and stir in the vanilla extract and sea salt. Set aside 1/3 cup of the caramel for topping.
04 -
In a large pot over low heat, melt the butter. Add the mini marshmallows and stir until almost completely melted. Add the remaining caramel sauce (not the reserved portion) and vanilla extract, stirring until smooth.
05 -
Remove from heat and immediately add the Rice Krispies cereal. Stir until all the cereal is coated with the marshmallow mixture.
06 -
Transfer the mixture to the prepared pan. Using a piece of parchment paper or wax paper lightly coated with cooking spray, gently press the mixture evenly into the pan. Do not press too hard or the treats will become dense.
07 -
Warm the reserved caramel sauce slightly if it has hardened. Drizzle it over the top of the Rice Krispie treats. Sprinkle with flaky sea salt.
08 -
Allow to cool completely at room temperature, about 1 hour. Use the parchment paper overhang to lift the treats out of the pan. Cut into squares and serve.