In a large mixing bowl, whisk together the cake mix, flour, sugar, and salt. Add in the rest of the ingredients and stir for about a minute until combined.

Bake for 17-20 minutes, or until toothpick inserted in center comes out clean. Remove from oven and allow cupcakes to cool in tin for 5 minutes before transferring to a wire rack to cool completely.

Combine the hot water and salt in a small bowl and stir until dissolved. Let mixture cool.

In the bowl of a stand mixer, fitted with a paddle attachment, or with a hand mixer in a large bowl, beat together the marshmallow creme and the shortening until combined.

Add in the powdered sugar and vanilla and mix on high speed until fluffy--about 2 minutes.

Add the salt solution to the mixture and mix until combined.

Transfer filling to a pastry bag fitted with a tip.

In a medium bowl, stir together all of the ingredients until no lumps remain.

In the bowl of a stand mixer, stir together the powdered sugar, butter, milk, and vanilla until light and fluffy. Add in a few drops of food coloring (any color) and stir until you've reached the desired color.

Transfer icing to a pastry bag fitted with a small round tip**

Once the cupcakes have cooled, push the tip of your pastry bag with the filling into the center of the cupcake and squeeze the filling out as you slowly pull the tip out. Smooth down any filling that is sticking out with a butter knife or offset spatula.

After all the cupcakes have been filled, dip the top of each cupcake one at a time into the glaze. Allow excess glaze to drip off and place on a wire rack or baking sheet. Refrigerate dipped cupcakes for ten minutes, allowing to set. Remove cupcakes from refrigerator and dip a second time. Return cupcakes to the refrigerator, allowing the glaze to set up once again.

Once cupcakes have set, you are ready to pipe on the icing. Using your pastry bag, draw curls across the top of the cupcake.