Melt butter in a large saucepan over medium-high heat. Stir in marshmallows and melt completely. In a large mixing bowl, pour the crushed chips, followed by the melted marshmallow and mix together thoroughly (take care to use utensils while mixing – the melted marshmallows are HOT!). Fold in the chocolate drops, and then press the mixture into a 9" x 13" baking pan (you can use 9" x 9" if you like your bars super dense). Let cool (place in freezer for 5 minutes to expedite); cut and serve.