Pulse serrano, garlic and ginger in a food processor until minced. Scrape down the sides and pulse again. Add onion; pulse until finely chopped, but not watery.
Heat oil in a large saucepan over medium-high heat. Add the onion mixture and cook, stirring occasionally, until softened, 3 to 5 minutes. Add coriander, cumin and turmeric; cook, stirring, for 2 minutes.
Pulse tomatoes in the food processor until finely chopped. Add to the pan along with salt. Reduce heat to maintain a simmer and cook, stirring occasionally, for 4 minutes. Add chickpeas and garam masala and reduce heat to a gentle simmer; cover and cook, stirring occasionally, for 5 minutes more. Serve topped with cilantro, if desired.