Many home cooks panic at the thought of making a caramel syrup, but actually, it’s remarkably easy. In the simplest of terms, when sugar with a little water boils down, you’re left with a perfectly clear sugar syrup. As the syrup continues to boil, the water evaporates away and the sugar starts to caramelize, eventually turning a deep amber color. To line a flan dish, this amber syrup is poured into a baking dish or pan and swirled around until it thickens and coats the interior of the dish. The secret to producing a never-fail caramel syrup is the right type of pot. A heavy-bottomed saucepan, specifically with a light-colored interior, lets you view the true color of the mixture as it boils, thickens, and caramelizes. This type of pot not only removes the need for a candy thermometer, but the heavier pan will greatly reduce the risk of scorching the mixture from the bottom. I recommend an enamel-coated cast iron saucepan (by Le Crueset), preferably one with a spout.
To prepare caramelized sugar syrup: Bring a kettle of water to a boi. Place a cup of boiling water next to the stove and insert a pastry brush into the water. Reduce heat under kettle to low and simmer until needed for clean-up. Place water and sugar (as specified in your recipe) in a heavy-bottomed saucepan with a light interior. Stir gently, using the stem of a wooden spoon, taking care to keep the sugar granules off the sides of the pan. Place pot over medium heat and dissolve sugar, gently swirling the pan occasionally. When the mixture is perfectly clear, raise heat and bring it to a boil. Let mixture boil (uncovered and without stirring or swirling) until syrup becomes a deep amber color, similar to a rich cup of tea, 5 to 10 minutes. If at any time during boiling, sugar crystals cling to the sides of the pan, use the wet pastry brush to wash them away. (This prevents the clinging sugar from burning and falling into the syrup, which would adversely affect both its flavor and consistency.) While syrup is boiling, stay close by. Once you smell the savory aroma of caramel, the syrup will color quickly. (Put on your oven mitts—the syrup is dangerously hot!) When it’s ready, remove from stove and immediately pour it into a baking dish or use as directed in recipe. Then quickly pour simmering water into the saucepan and swirl to dissolve and release any sticky syrup before it hardens. See, you did it!