It worked great!! I used
Promise, what is what I had on hand. 'Didn't feel like going out and getting a $4 can of Crisco for what I needed - about a tablespoon.
It worked fine. I really didn't even notice any color at all. The only problem I had was when a fly took direct aim at the melted marshmallow mixture as I poured it out over the powdered sugar. Luckily, he landed on the edge, so I just threw that little bit away ;o)
When I began kneading, I didn't think it would ever "come together" but after about 5 minutes, it did. I didn't need to add anymore of anything, and in fact I had some powdered sugar left over on my work surface. I guess the marshmallow just "took what it needed" and as it cooled it became a little more solid too. I didn't think those gooey strands would ever turn themselves into a ball!
I'll take a picture of my final product once I make the cupcakes. Thanks! It gave me an idea for my next frosting too... melted marshmallows look exactly like boiled frosting. 'Next time!