As recommended in the blog on failsafe management for colds and flu

3 cups sugar
1 cup water
1 tsp citric acid

Put water, sugar and citric acid in a heavy saucepan. Stir over a low heat until sugar is dissolved.  Increase heat, boil rapidly for approximately 15-20 minutes (20 mins for hard toffee, the mixture will turn slightly brown) or until a small amount of mixture will crack when tested in cold water. Remove toffee from heat, allow bubbles to subside, pour into paper patty cases.