Pour the vinegar and water into a clean pan, add the sugar and boil for fifteen minutes. Add the butter in little bits, and boil for another fifteen minutes. Have ready a plate greased with butter, turn out the toffee on it and sprinkle on the vanilla essence. Turn the edges inward (as if folding them) when cool enough to handle, smear the fingers with butter and hang the mixture over a hook. Pull the toffee lengthways, then hang it up again and again for 8-10 minutes until it is all white, or streaked with white. Then twist in sticks about three-quarters of an inch thick, and before it can set, cut into half-an-inch and one inch lengths with a pair of scissors. Place on greased paper to harden.