Simmer your herb in the water for 20 minutes—keep the pot covered. Strain and return infused water to the pot. Add sugar and honey, stir, and bring to a boil. Simmer gently.
Next, clip on your candy thermometer and boil to 330 degrees. This is the tricky bit—keep stirring as the temperature rises. As it gets close, let the syrup drip from your (wooden) spoon; if it forms a thread, then allow a drop to fall into a cup of cool water.
Now the fun part—bite that little drop of syrup. Is it gooey and sticking to your teeth? Keep cooking. If it cracks when you bite it, you’re done. Take that puppy off the heat.
Now, if your syrup starts to crystalize, just add a cup of water and an extra tablespoon of honey, scrape in the crystals, and start again.
When you’re at the hard-crack stage, line a baking sheet with parchment and pour the syrup in. Let it cool a bit, then score with a sharp knife—this allows the cough drops to break apart easily once cooled. Store by wrapping each in parchment paper or dust them with powdered sugar to keep them from sticking to each other.
Herb Cough Drops (easy version):