It’s funny that a recipe with only one ingredient can take almost two hours to make, but this is one recipe you do not want to rush or you’ll not get good results. This recipe came from the Eagle Brand web site. It’s a great dip for sliced apples, or it can be served as a caramel sauce over ice cream.
1 (14-ounce) can Eagle Brand Sweetened Condensed Milk (NOT EVAPORATED MILK)
Pour the milk into the top of a double boiler; place over boiling water. Over low heat (almost lowest setting), simmer 1 to 1-1/2 hours or until thick and caramel-colored, stirring occasionally. Beat until smooth.
NOTE: On the 2nd to lowest setting on our electric range, this took about 90 minutes to 2 hours.
The Family Recipe Box 
I love caramel and making it is a lot of fun too. I had a ball making these homemade caramel apples by Martha Stewart. Perfect for Halloween!
http://michaelbeyer.wordpress.com/2010/10/10/classic-caramel-apples/