Preheat oven to 450°F with pie plate or baking dish inside.
Once oven is preheated, use a pot holder to remove hot baking dish from the oven.
Place pat of butter in the baking dish and swirl to coat the bottom and sides.
Pour chocolate chips in an even layer into the bottom of the skillet.
Arrange marshmallow halves over the surface of the chocolate chips, covering the chocolate completely.
Bake for 5 to 7 minutes or until marshmallows are toasted to your preference (watch closely!).
Use an oven mitt to remove the skillet from the oven and allow to rest for 5 minutes.
Serve immediately with graham cracker squares or sticks.