Toast the Coconut: In a sauté pan set over medium-high heat, add the coconut and stir continuously for about 5–7 minutes until toasted to a golden brown. Reserve ½ cup for garnish.

Prepare the Dulce de Leche: Combine dulce de leche with milk in a microwave-safe bowl and heat for about 1.5 minutes, stirring halfway through, until smooth.

Combine Coconut and Dulce de Leche: Mix the majority of the toasted coconut into the dulce de leche until fully incorporated. Set aside.

Melt Marshmallows and Butter: In another bowl, combine marshmallows and butter. Microwave on high for approximately 2 minutes, stirring until melted and smooth.

Mix Cereal: Fold the Rice Krispie cereal into the melted marshmallow mixture until evenly coated.

Layer the Mixture: Grease an 8x12 inch pan. Press half of the cereal mixture into the bottom, then spread the coconut and dulce de leche mixture over it. Top with the remaining cereal, pressing down gently.

Chocolate Finish: Melt semisweet chocolate in short bursts in a microwave-safe bowl. Pour over the bars and spread evenly. Sprinkle reserved toasted coconut on top.

Set and Serve: Allow the chocolate to harden at room temperature for approximately 30 minutes before cutting into squares.