1. Mix sugar, cornstarch, salt, and cocoa powder in a medium sauce pan. Whisk in the water. Heat over medium heat until mixture gets thick and starts to boil.
2. Boil for 1 to 2 minutes. (Make sure you don’t boil too long, or it will start to harden and set like candy.) Remove from heat and stir in oil and vanilla.
3. Cool and spread on cooled cake/cupcakes. Enjoy!
Source of recipe: Um... I modified a recipe I saw somewhere.