Heat oil in a large pot over medium heat.
Add sliced onion and cook until tender, about 3-4 minutes.
Add chopped garlic and sliced jalapeño pepper. Cook for an additional minute.
Add chicken to the pot and cook until browned, about 5-6 minutes.
Pour in coconut milk and chicken broth. Bring to a simmer.
Stir in fish sauce, lime juice, grated ginger, and ground cumin.
Season with salt and pepper to taste.
Serve hot, garnished with chopped fresh cilantro leaves (if desired).
