How to make it
Heat oven to 350°F. Grind cardamom seeds with a mortar and pestle or spice grinder.
Heat 2 tbsp oil in a stockpot or Dutch oven over medium-high heat. Add onion and sauté until translucent, 4 to 5 minutes. Turn heat to medium-low and add garlic, cardamom, Kashmiri chili, turmeric, and garam masala and cook until fragrant, 30 to 45 seconds. Add tomatoes with their juices and cook, stirring occasionally, 3 to 4 minutes. Stir in chicken and cook for 2 minutes. Pour in the chicken broth and add corn and lime juice.
Increase heat to high and bring to a boil. Reduce heat, cover, and simmer gently until corn is tender, 10 to 12 minutes. Stir in salt and taste; adjust seasoning if necessary. Let soup sit, covered, for 10 minutes before serving.
While the soup is cooking, cut naan into 1⁄4-inch strips and drizzle with remaining 2 tbsp oil. Toast on a baking sheet in the oven until golden brown and crisp, 8 to 10 minutes. Remove from oven and cool for 5 minutes.
Reheat soup if necessary. Garnish with toasted naan strips, hard-boiled eggs, cilantro, scallion, and serrano chili. Serve hot.