So here is where we can get a little technical in our terms.  For the best ooey gooey marshmallows, use the mini marshmallows. They melt together into one glorious marshmallow.  For the best pillowy marshmallows, use the larger marshmallows. When I use them, I will evenly divide them onto the top of the sweet potatoes in rows so that everyone gets one pillowy marshmallow on top!