Combine sugar, milk and a dash of salt in a large saucepan. Boil over medium heat for 3 minutes, the mixture reaches desired thickness, or to a temperature of 234 ℉. Stir occasionally. While syrup is cooking, place butter, chocolate chips and vanilla in mixer bowl.
After sugar mixture is done, pour syrup into the chocolate and blend at low speed using the dough hook, then switch to medium speed for 10 minutes. Add in pecans during the last minute of mixing. Pour the fudge into an 8×8 pan lined with parchment paper. Chill until firm and then remove from the pan.