I am a big fan of s'mores, and would eat them year-round if it weren't unreasonable to make a big bonfire every day. My husband, on the other hand, is not at all a fan of s'mores, but loves cupcakes. And so, years ago, I did a search for s'mores cupcakes and came up with a ton of hits.
One recipe I found, used Martha Stewart's One-Bowl Chocolate Cupcakes as the base (recipe here) and used a buttercream frosting with marshmallow cream added to it. If you've got a buttercream recipe you love, I would just use that and then add the Marshmallow cream to it. In case you're interested, here's how I make it:
2 sticks unsalted butter, room temp
2 cups confectioner's sugar
a small amount of vanilla (I never measure, but probably around 1/2 tsp)
1 jar Marshmallow cream (7 oz)
Beat butter until light and fluffy. Slowly add the powdered sugar until incorporated. Add Marshmallow cream and vanilla. Continue beating until fluffy. Color with food coloring, if desired. This recipe will make enough to frost 24 cupcakes.
After I frost my cupcakes, I add a chocolate square and some graham cracker crumbs for garnish. You could make a graham cracker crumb crust for the cupcakes, too, and I bet that would be delicious.
These have become our standby cake and frosting recipe, making an appearance at every birthday, celebration, and even at our last Thanksgiving dinner. If you're craving some sweets, I'd highly recommend making these. If you do, let me know how they turn out, ok?