Butter the bottom of a 9×13 pan.
Melt 4 Tbsp butter completely and put it in a large, microwavable mixing bowl. Place marshmallows in over the butter and stir them around to coat. Microwave for 30 seconds, stir, then microwave for another 30 seconds and stir.
Pour cereal in the bowl and mix well with the marshmallows. Put the mixture into the 9×13 pan and wet down your hand with water to press the mixture evenly in the the pan. Cover and cool in the fridge for about an hour.
Cut into squares and place upside down on wax paper. Melt the white chocolate at 30 second intervals, stirring after each 30 seconds.
Dip the bottom third to half of each treat into the chocolate and place upside down on the wax paper to cool.