Heat oil in a large soup pot over medium-high heat. Add chopped onions and minced garlic and ginger. Add minced serrano, if desired.
Cook, stirring, for about 10 minutes, or until the vegetables soften and turn into a golden paste.
Stir in coriander, cumin, cayenne, turmeric and paprika.
Add tomatoes, cinnamon stick, amchoor or lemon juice. Stir together to combine.
Stir in chickpeas and 1/2 cup of chickpea broth, vegetable broth or water. Reduce heat to low.
Cover and simmer for 20 minutes. Remove cover and give mixture a stir. The sauce should be thick enough to coat the chickpeas. If it seems too soupy, continue cooking, uncovered for another 5 minutes or so.
Season with sea salt and freshly ground pepper, add chopped coriander or ginger, if desired, and serve.