Butter a large rimmed baking sheet or 9x13 pan thoroughly and set aside.
In a medium saucepan over high heat, combine sugar, salted butter, light cocoa, and evaporated milk.
Bring the mixture to a hard boil, stirring constantly.
Boil for 8 minutes once the hard boil is reached.
Add the chopped pecans to the pot and continue boiling for 2 more minutes.
Remove from heat and stir in the vanilla extract.
Pour immediately into the buttered pan and spread evenly.
Cool for 20 minutes, then cut into squares before the candy sets completely.