For this colorful Thai-inspired sweet potato stew, use your discretion with the hot seasoning you choose; a little will give a hint of heat, but if you want a spicier stew, you can step it up from there.
Heat the oil in a soup pot. Add the onion and sauté over medium-low heat until translucent. Add the garlic and continue to sauté until both are golden.
Add the sweet potatoes and water. Bring to a rapid simmer, then lower the heat. Cover and simmer for 10 minutes, or until the sweet potatoes are about half done.
Stir in the bell pepper, green beans, and ginger.
If using lemongrass, cut each stalk into 3 or 4 pieces, and bruise by making long cuts here and there with a sharp knife. This will help release the lemony flavor. Stir into the soup pot. Either way, simmer the stew for 10 minutes longer.
Stir in the coconut milk, peanut butter, salt, and curry paste or hot sauce. Return to a simmer, then cook over very low heat for 5 minutes longer, or until all the vegetables are tender and the flavors well integrated.
Remove lemongrass pieces, if used. Taste to adjust seasonings, particularly the hot seasoning if you’d like a spicier stew, as well as the salt and ginger.
Serve at once, topping each serving with a few cilantro leaves.