Place the molasses in a heavy aluminum saucepan or unlined copper saucepan and bring it to a boil over medium heat. Boil until the molasses reaches the hard-ball stage on a candy thermometer (250 to 266 degrees.) Remove it from the stove and add the butter and vanilla, stirring to mix them in. Pour the candy out onto a well greased piece of confectioner's marble or a well-greased heavy platter or baking sheet and allow it to stand until the candy begins to get hard around the edges. Moisten your hands with ice water. Take a 1/2 cup size ball of taffy into both hands and pull it back and forth until the taffy changes color and becomes golden. When the taffy begins to harden, twist it or braid it into sticks, tie it into knots, or shape it as desired.
Taffy and indeed most candies are weather sensitive. Pick a cool, dry day to make this recipe.
Recipe courtesy of Jessica Harris, "The Welcome Table"