Fit a disposable piping bag with a large star tip, like a 1M. Fill the bag with buttercream.
Pipe buttercream around the perimeter of a cupcake and then pipe another ring to mound up the buttercream.
Repeat with all of the cupcakes.
Decorate the Cupcakes:
Toast the waffles in the toaster. Allow them to cool to room temperature, then cut them into individual waffles.
Place 1 waffle into each cupcake, trying to position the best looking side of the waffle facing up. Make sure to push the waffle down into the buttercream so it stands up and is supported by buttercream on both sides.
Mix up some black royal icing powder with warm water to outline consistency. Transfer the icing to a piping bag fitted with a small round tip, like a #5.
Pipe a squiggly line across one cupcake to represent the strand of lights, then immediately press colorful M&M's (not brown), turned sideways, into the buttercream so they connect to the black strand at the top. Make sure the M&M's are evenly spaced.
Repeat with the remaining cupcakes. Chill the cupcake to set the royal icing and prevent it from bleeding into the buttercream.
Notes
Easy Vanilla Buttercream recipe HEREStore the cupcakes in the refrigerator in an airtight container. Bring to room temperature before serving.You're Gonna Bake It After Allbakeitafterall.com