For the Cupcakes

1. Preheat oven to 300°F (148°C) and prepare a cupcake pan with liners.
2. Add the dry ingredients to a large bowl and whisk together to combine. Set aside.
3. Whisk together the egg, milk, vegetable oil and vanilla in another medium-sized bowl.
4. Add the wet ingredients to the dry ingredients and mix until well combined.
5. Add the water to the batter and mix until well combined. The batter will be very thin.
6. Fill the cupcake liners a little more than half way and bake for 18-23 minutes, or until a toothpick comes out with a few moist crumbs.
7. Remove the cupcakes from the oven and allow to cool for 2 minutes, then transfer to a cooling rack to finish cooling.

For the Filling

1. When the cupcakes are cool, make the filling. Add the butter to a mixer bowl and beat until smooth.
2. Add about half of the powdered sugar and mix until well combined and smooth. It may take a few minutes to incorporate, but it will.
3. Add the remaining powdered sugar and mix until well combined and smooth.
4. Add the marshmallow creme and stir until well combined.

To Assemble

1. To fill the cupcakes, cut out the centers of the cupcakes. You can use a cupcake corer or a knife.
2. Fill the centers of the cupcakes with the filling and replace the core of the cupcake that you removed on top of the filling. I cut a little bit of the core off before placing it back on top, since there’s a filling there now and you don’t need all of that cake core.
3. To make the chocolate ganache topping, add the chocolate chips to a medium sized bowl.
4. Heat the heavy whipping cream just until it begins to boil, then pour it over the chocolate chips. Allow it to sit for 2-3 minutes, then whisk until smooth.
5. Spread the chocolate ganache onto the top of each cupcake, all the way to the edges. If it starts to cool and get a bit firm, heat it back up for 5-10 seconds, until spreadable again.
6. To make the icing for decorating on top, beat the butter in a mixer bowl until smooth.
7. Add the powdered sugar and mix until evenly combined. It’ll be lumpy and dry.
8. Add the milk and vanilla extract and mix until everything comes together and smooths out.
9. Pipe the loop design on top of each cupcake using a small round tip. I used Wilton tip 3.
10. Refrigerate the cupcakes until ready to serve. Serve cool but not cold.