1 cup light brown sugar, firmly packed
2/3 cup light corn syrup
1/4 cup butter
2/3 cup evaporated milk
1/8 teaspoon baking soda
1 teaspoon vanilla

In a medium saucepan combine sugar, syrup, and butter.
Cook, stirring constantly, over medium heat until sugar has dissolved and mixture comes to a full rolling boil.
Allow to boil, without stirring, for exactly 1 minute.
Remove from heat and let stand for 5 minutes.
In another bowl or large measuring cup, combine evaporated milk, baking soda, and vanilla.
Stir into the slightly cooled sauce.
Pour into jars, cover, and refrigerate.
Place jar in a pan of warm water to reheat when ready to use.
Makes 2 cups of butterscotch sauce.