Wash sesame seeds and remove any debris that may be in the seeds and drain well. Heat a cast iron skillet over medium high heat until a drop of water bounces around the skillet. Pour seeds into skillet and stir constantly. Dry and parch seeds until light brown, approximately 2 minutes. Do not burn seeds.
In a heavy saucepan, combine and melt the sugar, butter, milk and vinegar. Using a wooden spoon, stir constantly until ingredients are dissolved. Cook over medium high heat to light crack stage. If using a candy thermometer, the temperature should be between 265 and 285 degrees F. Once it reaches the desired temperature, remove from heat and beat in the sesame seeds with your spoon. Pour immediately into prepared dish. Score candy while still warm and cut into squares when cool.