Put the popcorn in a very large buttered bowl, removing any unpopped kernels.

In a saucepan over medium heat, stir the brown sugar, corn syrup, butter and salt until the butter melts.

Bring to a full rolling boil and boil 2 minutes without stirring.

Carefully pour the hot syrup over the popcorn and toss with a buttered spoon until coated. Stir in candy if using.

Let cool 1 to 2 minutes, until safe to handle. With buttered hands, press into 3-inch balls.

Set on wax paper to firm up, then wrap individually.