5 1/2 cups popcorn, popped without salt or fat (this is about one large bag of microwaveable popcorn)
1 1/2 cups sugar
6 tablespoons light corn syrup
1/4 cup water
3 tablespoons molasses
1 tablespoon butter
1/2 teaspoon baking soda
1/2 teaspoon vanilla extract
1/4 teaspoon salt
Line a baking sheet with foil; coat foil with cooking spray. Alternately, line a baking sheet with a silicone baking mat. Set aside.
Place popcorn in a large zip-top plastic bag; seal. Crush popcorn using a meat mallet or rolling pin; set aside.
Combine sugar, syrup, and water in a medium saucepan over medium heat.
Cook 1 minute or until sugar dissolves, stirring constantly. Cook, without stirring, until candy thermometer registers 270? (about 8 minutes). Stir in molasses and butter (sugar mixture will bubble up and gurgle);cook until thermometer registers 290? (about 5 minutes).
Stir in baking soda, vanilla, and salt.
Stir popcorn into boiling syrup mixture.
Working quickly, pour popcorn mixture onto prepared pan; spread to 1/4-inch thickness using a wooden spoon coated with cooking spray (make sure to head this warning ? you will not be able to spread the mixture if you don?t coat the spoon with cooking spray).
Cool completely; break into large pieces.
Note: Store brittle in an airtight container at room temperature for up to four days.