In a medium saucepan, over medium heat, melt the unsalted butter. Allow it to bubble, swirling occasionally until it turns a golden brown and has a nutty aroma. Remove from heat and add a pinch of salt.

Immediately stir in the marshmallows until they are completely melted and well combined with the brown butter.

Once the marshmallows have melted, add the Rice Krispies to the saucepan. Gently fold them into the marshmallow mixture until evenly coated.

Drizzle the dulce de leche over the cereal mixture, followed by the vanilla extract. Stir gently until the mixture is fully combined.

Transfer the mixture to a greased 9x13 inch baking dish. Press it down firmly using a piece of parchment paper.

Let the treats cool in the pan for at least 30 minutes before slicing into squares.