Spray a 9x13" pan with cooking spray and line with parchment paper. Set aside.

Place sugar, water, and white corn syrup in a 12 cup or 3 L saucepan over medium heat and cook stirring until the sugar dissolves.

Bring to a boil, and cook without stirring. Brush down the crystals on the sides with a pastry brush dipped in cold water. Cook until the hard crack stage of 300F or when 1 tsp. is dropped into water it forms hard brittle threads about 10 min.

Remove from the heat and being very careful to add baking soda. Add it all at once and quickly stir with a whisk. It will increase dramatically but just keep whisking, add the vanilla in now.

Working quickly pour toffee into the prepared pan. Let cool without disturbing until completely cool about 2 hours. Break into pieces.

Make ahead, store in an airtight container between layers of waxed paper for 1 month.