You will need a candy thermometer. If you don't have one, have a cup of cold water available to drop the mixture in....soft ball stage will drop in, stay together and stay soft. If it is runny or stringy, it is not hot enough.
If you get it too hot, it will hit the hard ball stage, which is exactly what it sounds like. Drop a bit of the candy in and it will form a hard ball. If you get there, stop the heat and deal with hard carmals. They will still be dilicious, just not soft.
You want it to be creamy and soft and delicious. Melt in your mouth soft.
1 teaspoon plus 1 cup butter, divided (1/2 cup plus 1/2 teaspoon)
1-1/4 cups packed brown sugar
1 cup sugar
1 cup light corn syrup
1 can (14 ounces) sweetened condensed milk
In a large saucepan,(*****if you have a tempermental stove top, use a double boiler so you have less of a chance of burning this. I always use a double boiler because I tend to try to hurry things along. With this recipe, slow is good)
Combine the sugars, salt and remaining butter. Bring to a boil over medium heat, stirring constantly. Stir in corn syrup; return to a boil. Remove from the heat; slowly stir in milk.
1 teaspoon vanilla extract
Cook and stir over medium-low heat until a candy thermometer reads 238° (soft-ball stage). Remove from the heat; stir in vanilla. Pour into prepared pan. Cool. Using foil, lift candy out of pan; cut into 1-in. squares. Wrap individually in waxed paper. Yield: 2-1/2 pounds.