Aunt Ruby's Caramels

This is my ex mother-in-law's recipe, and very tasty!  I STRONGLY urge you to use a candy thermometer.  You can pic one up at a good Kroger or Super Wal-mart very reasonably!

Ingredients: 
1c. butter
1 lb light brown sugar
1c. light corn syrup
1 (15 oz) can Sweetened Condensed Milk
1 tsp vanilla (optional)
Chopped nuts (optional)

Directions:
     In a 2 qt saucepan, melt butter slowly.  While butter is melting, butter a 9x13 baking pan and set aside.  Stir in sugar and syrup and mix well.  Add condensed milk , stirring constantly (stove should be on med to med-high heat).  Continue stirring and cook to 240 degrees (soft ball stage).  It will take a while to get to the correct temp.  Be patient and keep stirring.  If you turn the heat up, the butter and sugar will scorch.  When caramel reaches 240 degrees, remove from heat and stir in nuts and vanilla, if desired.  Pour immediately into the buttered baking pan.  Be careful if you want to lick the spoon or thermometer!  They are still very hot,but you will know right away if it is going to turn out right!  When caramel has cooled, cut into squares and wrap in wax paper or dip in chocolate. I also had a friend at work tell me that you can dust cornstarch over undipped caramels to keep them from sticking together, but I have not tried that yet.