Hard candy such as lollipops and peanut brittle must reach a high temperature, known as the hard crack stage, when cooking. Otherwise, they come out soft and gooey, like fudge. The ingredients for hard crack candy are fairly simple, but you can vary the recipe by adding different colors and flavors.
Prepare a marble slab, candy molds, miniature muffin pans or a cookie sheet to hold and shape the hot candy. Place parchment paper on the slab or on an upside-down cookie sheet. Spray the parchment paper, muffin pans or molds with nonstick cooking spray.
Bring one cup of water to a boil in a large, heavy pan. Turn off the heat and add 2 cups sugar, 2/3 cup light corn syrup and 1/2 tsp. cream of tartar to the hot water. Stir with a wooden spoon until dissolved.
Bring the mixture to a boil and then briefly place the lid on the pot so that the steam can wash away any sugar crystals that may have formed on the sides of the pan. Once the mixture begins to boil, don't stir it. Remove the lid and place a candy thermometer in the pot, making sure that it doesn't come into contact with the bottom or sides of the pot. Allow the mixture to boil until it reaches the hard crack stage at 300 degrees F. Test to be sure the syrup has reached this stage by dropping 1 tsp. of the hot syrup into 1 cup cold water. The cooled syrup should become brittle, hard threads that break when bent.
Turn off the heat and let the syrup cool to approximately 160 degrees F. Add a few drops of food coloring in the desired color and one of the following flavors. Add 1/4 tsp. oil-based flavorings such as peppermint, cinnamon or anise, or 1 tsp. alcohol-based flavors such as vanilla, lemon, orange, almond or butterscotch. Optionally, add 1 tsp. citric acid to give a sour flavor to fruit-flavored hard crack candies.
Pour the mixture into the molds or muffin cups, or pour small circles onto the cookie sheet or marble slab and roll into round balls. You can also pour one large sheet of syrup onto the slab and cut it into squares with a pair of sharp kitchen shears. Allow the candy to cool and harden completely. Wrap each piece of hard crack candy individually in plastic wrap and store in a cool, dry place.