Brown the Butter: In a large saucepan over medium heat, melt the butter. Continue cooking, stirring frequently, until the butter turns a golden brown color and has a nutty aroma, about 5-7 minutes. Be careful not to burn it.

Add Marshmallows and Dulce de Leche: Remove the saucepan from the heat. Immediately add the marshmallows and dulce de leche to the browned butter, stirring until completely melted and smooth.

Combine with Rice Krispies: Add a pinch of salt and the Rice Krispies cereal to the mixture. Stir until the cereal is fully coated with the marshmallow mixture.

Press into Pan: Lightly grease a 9x13-inch baking dish or line it with parchment paper. Pour the mixture into the prepared dish and press it down evenly with a spatula or your hands (greasing them lightly will help prevent sticking).

Cool and Cut: Allow the treats to cool at room temperature for about 30 minutes before cutting them into squares.

Optional Toppings: Drizzle extra dulce de leche over the top and sprinkle with sea salt for an added touch of sweetness and flavor, if desired.