This is a recipe I found on a blog "bake at 350" but I modified it a bit by using a cake mix. Tasted good to our fam! And let's be honest... it's all about the marshmellow filling.
For the Cupcakes:
Chocolate cake mix (or see link above)
For the Filling:
4 tablespoons unsalted butter, at room temperature
1 cup powdered sugar
2 teaspoons pure vanilla exrtact
3 tablespoons heavy cream
1 cup marshmallow creme
For the Ganache:
6 ounces bittersweet chocolate, chopped
1/2 cup heavy cream
1 tablespoon unsalted butter
2 teaspoons pure vanilla extract
For the Icing:
1 stick unsalted butter
1 & 1/2 - 2 tablespoons milk
2 cups powdered sugar
1/4 tsp vanilla
Prepare and bake the cupcakes (using paper liners).
For the filling: Using a mixer, cream the butter until light and fluffy. Beat in 1/2 cup confectioners’ sugar. Add the vanilla and 1 tablespoon heavy cream; beat until smooth. Beat in the remaining 1/2 cup confectioners’ sugar and 2 tablespoons heavy cream in batches, alternating after each addition. Beat in the marshmallow creme; set aside or refrigerate.
For the ganache: Place the chocolate in a stainless-steel bowl. Heat the cream and 1 tablespoon butter until just boiling, then pour over the chocolate; let stand for 5 minutes. Whisk until smooth. Add 2 teaspoons vanilla; let stand until cool but still glossy and liquid.
Spoon the filling into a pastry bag with a medium star tip. Insert the tip into the center of each cupcake top; fill until the cupcake is heavier (do not overfill). (It's OK if some of the filling peeks out, it will be covered by the ganache.)
Spoon a little ganache on each cupcake and lightly spread with an offset spatula or a knife. (I also found that dipping the cupcake in the ganache worked quite well.) Chill for at least 15 minutes.
Meanwhile, prepare the icing: Using a mixer, beat the remaining 1 stick butter, 1/4 teaspoon vanilla, the milk and confectioners’ sugar until smooth, adding more milk if needed. Spoon into a pastry bag with a small tip (I used a #2 plain tip); pipe onto the cupcakes to decorate.
Store in the refrigerator.