In a medium bowl, whisk to combine flour, corn starch, cocoa powder, and salt. Set aside.
Using a stand mixer or handheld mixer, beat butter and sugar together until light and fluffy. Add in egg and vanilla and continue to mix until well blended.
Gradually add in the flour mixture, mixing after each addition.
Roll the dough into a log with a diameter of about 1 ½ inches. Wrap with parchment or wax paper and place in the refrigerator to chill for 1 hour.
When ready to bake, preheat the oven to 350 °F and line baking sheets with parchment paper or silicone liners.
Carefully slice the dough into ¼- ½ inch slices and place them on the baking sheet.
Bake for 8-12 minutes, or until set. Remove from the oven and allow to cool on the baking sheet for 2-3 minutes, then transfer to a cooling rack to cool completely.
To decorate:
In a large bowl, beat butter until light and fluffy. Slowly mix in the powdered sugar, about ½ cup at a time. Add cream and vanilla and mix until well combined.
Using a piping bag, pipe frosting in strips across the cookies creating “mummy wrappings” use a small dot of frosting on the back of each eyeball to secure them to the cookies.
Notes
Allow the cookies to sit on the countertop to allow the frosting to harden up a bit before placing them in an airtight container until serving.As a shortcut, you can use store-bought cookie dough and/or ready-to-spread frosting.