While the cupcakes are baking/cooling, in a large glass bowl, melt the chocolate in the microwave. Add the salt and mix until the chocolate is smooth. Add the butter and whip using a hand mixer until combined. Scrape the sides and bottom of the bowl with a spatula. Sift in the black cocoa powder and mix on low until combined. Add the 1 cup of powdered sugar and mix well. Add the remaining ¾ cup of powdered sugar and mix. Scrape the sides and bottom of the bowl with a spatula. Add in the vanilla, about 4 drops of black food coloring, and milk (as needed if the frosting is too thick) and mix very well until combined. If the frosting looks light gray add a few more drops of the coloring and mix well (it won't look black yet). Let the frosting sit while the cupcakes continue to cool so that the color can fully develop (takes 30-60 minutes).
To make chocolate bat wings: add about ¼ cup of chocolate chips to a small glass bowl, along with a little spoon of coconut oil and melt in the microwave. Add a drop or two of black food coloring and mix well. Transfer to a small piping bag and snip the tip off of the bag. Pipe bat wings on parchment sheets and let them set until hardened or chill them in the fridge.
After the frosting color has darkened, transfer to a piping bag fitted with your desired piping tip. Pipe swirls or what ever you want onto the completely cooled cupcakes. I stuck bat wings in the swirls to decorate. Have fun decorating however you wish and enjoy! Happy Halloween!!