There are a handful of resources on how to make curry paste from scratch, and if you are looking for extra credit, go ahead with that step because it would be great to have on hand (you can freeze it!). For the sake of ease, I am combining some fresh aromatics, like lemongrass and jalapeño, in tandem with a prepared curry paste, just to brighten it up. You can find curry paste at larger grocers or health food stores, as well as online. The Thai Kitchen brand is milder than the Mae Ploy brand, so adjust accordingly. Start with the two tablespoons called for and go up from there. If you can only find red or yellow curry paste at the store, go with that. Yellow is usually a bit sweet, and red a bit spicier, but any of them will work here. Your broth will just be a different color.