Mix on low speed until the mixture is crumbly and gradually add in the milk about 1 tablespoon at a time. Stop adding milk just as soon as the frosting comes together and is no longer dry and crumbly.
3 to 4 Tablespoons milk
Increase the speed to high and mix for about 30 seconds to fluff up the frosting.
Decorate
Transfer the frosting to a piping bag. If using a tip, use a basket weave design but use the smooth side (tip number 48 or similar). If you don't have a piping tip, just cut a small hole in the end of the bag and pipe away.
Attach the candy eyes first by placing a small dab of frosting where you want the eyes to go and set the candy eyes.
24 Candy eye balls
Then pipe the frosting on the top of the cupcakes in a criss-cross pattern to create the mummy appearance.
Notes
If you do not have buttermilk, you can also use regular milk and add 1 teaspoon vinegar to the milk before mixing into the recipe.
You can substitute boxed chocolate cupcakes and store-bought white icing if you prefer.
Cupcakes can be stored in an airtight container in the fridge for 3 days or frozen for 3 months.