To test if toffee is ready to your liking , have a glass of cold water ready , if you want stick Jaw , after the 15 minutes , drip a droplet into the water and it will set as soon as it hits the water but once you remove the droplet from the water it is still stretchy (chewy) . For hard toffee , then after the 20 minutes , drip a droplet into the glass of cold water and if it sets as soon as it hits the water and when it's removed it cracks when hit on a hard surface (crunchy) .