1 cup packed brown sugar
1/4 cup light corn syrup
1 cup water
1/4 teaspoon salt
1/3 cup butter
1/4 teaspoon vanilla extract

Put sugar, corn syrup, water and salt into saucepan. Stir over low heat until sugar is dissolved. Increase heat and cook until thermometer registers 250 degrees F, firm ball stage. Add butter; cook with occasional stirring until thermometer registers 300 degrees F (brittle stage). Remove from stove; add vanilla extract; pour into buttered shallow pan, making a layer 1/4 inch deep. While warm, crease into squares with a blunt knife. When cold, break into pieces.