Heat the olive oil over medium-high heat. Add the curry leaves, toss to coat with oil, and fry until it is fragrant and just starting to crisp - 20 seconds or so. Add the mustard seeds and when the seeds begin to pop a bit, stir in the cumin seeds. It should start to toast pretty quickly, and at that point, stir in the garlic-ginger paste along with the serrano chiles. Sauté for another minute or so, remove from heat, and immediately stir in the chile powder and turmeric.