Lightly butter a 9x13-inch (3-L) pan or coat with cooking spray.

In a large bowl, stir Rice Krispies with cornflakes and coconut.

In a large saucepan over medium heat, melt 1/4 cup butter. Add marshmallows and stir until melted, about 5 minutes. Or place butter in a large microwave-safe bowl and microwave for 30 to 60 seconds or until melted. Stir in marshmallows. Microwave on high for 1 to 1 1/2 minutes or until smooth when stirred.

 Add marshmallow mixture to cereal mixture. Stir well.

Then, place chocolate chips and 1/2 cup butter in a saucepan over medium-low heat. Stir often until chips are melted and mixture is smooth, about 5 minutes. Or place chocolate chips and butter in a microwave-safe bowl and microwave on medium, uncovered, for 1 1/2 to 2 minutes, until almost melted. Remove and stir until smooth.

Spread half of cereal mixture in bottom of buttered pan. Wet your hands and firmly press into an even layer. Evenly spread on all of the filling. Top with remaining cereal mixture, again pressing into an even layer.

Place uncovered pan in the refrigerator until set, about 45 minutes. Cut into squares. Store in a sealed container in layers separated by waxed paper. Squares can be refrigerated for up to 1 week.