1. In a heavy 2-quart saucepan combine sugar, corn syrup, and 1/2 cup water. Cook and stir over medium-high heat till mixture boils. Clip a candy thermometer to the side of the pan. Reduce heat to medium; continue cooking without stirring, till the thermometer registers 260°F, hard-ball stage (10-15 minutes).
2. Remove pan from heat; remove thermometer. In a large mixing bowl beat egg whites with a free-standing electric mixer on medium speed till stiff peaks form (tips stand straight). Gradually pour hot mixture in a thin stream over whites, beating on high speed about 3 minutes; scrape sides of bowl occasionally. Add vanilla and, if desired, food coloring. Continue beating on high just till candy starts to lose its gloss (5 to 6 minutes). When beaters are lifted, mixture should fall in a ribbon that mounds on itself.
3. Drop a spoonful of candy mixture onto waxed paper. If it stays mounded, the mixture has been beaten sufficiently. If mixture flattens, beat 1/2 to 1 minute more; check again. If mixture is too stiff to spoon, beat in a few drops hot water till candy is a softer consistency. Immediately stir in fruit or nuts. Quickly drop remaining mixture onto waxed paper. Store tightly covered.