Use 2 1/2 cups chocolate buttercream icing. Tint black and use for all decorating.
For eyes, inside of helmet, nose opening and inner chin area, pipe in with tip 3. Pat smooth with finger dipped in cornstarch
For outlines on inner chin area, pipe outlines with tip 2.
For outlines on helmet areas, eyes and face areas (except mouth), pipe outlines with tip 3.
For outlines inside mouth and around mouth, pipe outlines with tip 5.
For zigzags in inner chin area, pipe zigzags with tip 1.
For remaining areas of cake, pipe stars with tip 16.
For bolts at end of cheek lines, pipe dots with tip 5.