01 - Melt unsalted butter in a large saucepan over medium heat. Add mini marshmallows and stir continuously until fully melted and smooth.
02 - Remove saucepan from heat. Add Rice Krispies cereal and gently fold until evenly coated with the marshmallow mixture.
03 - Press mixture evenly into an oiled 9 x 13 inch baking dish, using a spatula or parchment paper to smooth the surface.
04 - In a separate saucepan, melt granulated sugar over medium heat, swirling gently until liquefied and amber in color. Add unsalted butter and stir thoroughly. Pour in heavy cream slowly while whisking until smooth. Remove from heat and mix in sea salt.
05 - Pour warm salted caramel evenly over pressed cereal base. Allow to set for several minutes, then sprinkle with flaky sea salt.
06 - Let treats fully cool at room temperature. Slice into squares before serving.