Cut leftover idlis into bite-sized pieces for easy cooking and coating.
Heat oil in a pan, add mustard seeds, and let them splutter.
Sauté chopped onions, green chilies, and curry leaves until fragrant and golden.
Add tomatoes, turmeric, red chili powder, and garam masala, then cook well.
Toss in idli pieces, mix gently, and coat evenly with spicy masala.
Cook for a few minutes until idlis absorb flavors and turn crispy.
Garnish with fresh coriander and serve hot with chutney or yogurt.