2 cups firmly packed brown sugar
1 cup granulated sugar
1 tablespoon white corn syrup
3/4 cup milk
1 tablespoon unsalted butter
1 teaspoon vanilla extract
1 1/2 cups chopped walnuts
Place sugars, syrup, milk and butter in saucepan over medium heat. Cook, stirring constantly, until sugar dissolves.
Clip a candy thermometer to the side of the saucepan. Continue cooking, without stirring, until mixture reaches soft-ball stage (240 degrees F).
Remove from heat.
Stir in vanilla extract and nuts.
Beat until mixture is very thick and has begun to lose its gloss.
Pour into a generously-greased 8-inch square pan or mound on wax paper.
Let cool for at least 1 hour.