Heat coconut oil in a pot over medium heat. Sauté onion, garlic, and ginger for a minute or two.
Add lime zest, broth, coconut milk, and kaffir lime leaves. Bring to a gentle simmer.
Add mushrooms and tofu. Simmer for 10 minutes.
Stir in soy sauce, lime juice, and sugar. Taste and adjust seasoning.
Add spinach or bok choy, cooking until just wilted.
Remove kaffir lime leaves before serving.
Serve hot, garnished with cilantro, lime wedges, and sliced chili.
