A candy thermometer is a must for preparing this rich, buttery treat. The syrup mixture bubbles up when you sprinkle it with baking soda, so use a long-handled spoon for stirring. Because the toffee holds well at room temperature, it also makes a good gift.
1 cup sugar
1/2 cup light-colored corn syrup
1/4 cup butter, cut into small pieces
1 tablespoon water
1/4 teaspoon salt
2 teaspoons vanilla extract
1/2 teaspoon baking soda
1 ounce semisweet chocolate, coarsely chopped
How to Make It
Line a baking sheet with foil; lightly coat foil with cooking spray. Lightly coat a metal spatula with cooking spray; set aside.
Combine sugar, syrup, butter, water, and salt in a medium saucepan. Bring to a boil over medium-high heat, stirring occasionally with a wooden spoon until ingredients are just combined. Cook, without stirring, until candy thermometer registers 300° (about 5 minutes).
Remove from heat. Stir in 2 teaspoons vanilla. Sprinkle 1/2 teaspoon baking soda over surface of mixture; carefully stir baking soda into mixture. Immediately pour sugar mixture onto prepared pan. Working quickly, spread to about 1/8-inch thickness using prepared spatula. Let stand for 2 minutes. Sprinkle chocolate evenly over toffee, and cool completely. Break into bite-sized pieces.
Note: Store toffee in an airtight container at room temperature for up to one week.