Add Karo Syrup, evaporated milk, and Hershey's Cocoa. Stir and mix well with a big wooden spoon. Add Sugar.
Briefly turn heat to high and bring to a FULL ROLLING BOIL, (stirring constantly). A boil that you CAN NOT Stir down. REDUCE HEAT TO MEDIUM HIGH and boil 4 minutes...Measure time accurately by the clock.
Remove from the heat and beat with mixer on high until thick and creamy. Add Vanilla.
Spread between cake layers, on top and sides. This will frost 10 layers.
With remaining icing heat to a rolling boil,turn off remove from burner. Continue beating until thick and creamy. Add 2 cups of chopped nuts. Pour on to a buttered pan. Let cool then cut into squares.
OR, YOU CAN EAT THE ICING WITH THE BIG WOODEN SPOON RIGHT FROM THE PAN.