Herb stems are packed with flavour, so rather than tossing them in the trash or compost, use them to make oils, vinegars and stocks tastier.
Image from Health Gauge.
Put your herb stems in a neutral oil (olive, grapeseed or canola, for example) or into white vinegar for at least a few hours. You can leave them in for a couple days to infuse more flavour, but not so long that they start to go off. This is an especially great way to use up "hard" herb stems that are noticeable in food so they're often left out, like thyme or rosemary stems.
Flavouring stocks is just as easy. Just put the herb stems in a sachet of cheesecloth, or even a coffee filter and submerge it in the stock for a few hours. "Soft" herbs work best here, like basil, sage and coriander. Either way, you save something useful from the bin, and get even more fresh flavour in all of your dishes.
7 Reasons You Shouldn't Throw Away Herb Stems [The Kitchn]