I'll get right to the point: TWO LARGE MARSHMALLOWS!
In the past, I was only roasting (toasting?) one marshmallow per s'more and I was always sort of disappointed in the end product. But this year, I started roasting two at a time. What a difference! The chocolate melts because there's enough heat to make it actually gooey! It's completely delightful.
If, like me, you've been skimping on the marshmallows, give this method a try. Yum!