Grandma Moore's Caramel Corn

My grandma use to make this and then press it down into a cake pan. We would tear off big chunks of the soft, gooey popped corn. It's addicting!

Fill a giant bowl with 12 quarts popped popcorn. (If I am in a hurry, I use microwave popcorn with no butter added).
In saucepan combine:
2 c. brown sugar
1 c. karo syrup
1 can sweetened condensed milk
1 square butter or margarine
Bring to boil. Boil for 3 minutes. Pour over
popped corn and mix to coat. Spread on a
buttered cookie sheet to cool.