In a large saucepan, heat the canola oil. Add the coriander seeds, cinnamon stick, allspice berries, turmeric, cracked black pepper and dried chile and cook over moderate heat until fragrant, about 1 minute. Add the shallot and ginger and cook, stirring, until softened, about 2 minutes. Add the water and bring to a boil over moderate heat. Cover and simmer for 20 minutes. Add the corn and simmer, uncovered, until tender, about 5 minutes.
Meanwhile, in a small skillet, toast the ground cumin over moderate heat until fragrant, about 10 seconds. Scrape the cumin into a small bowl and let cool. Stir in the chaat masala, salt and cayenne.
Brush the corn with melted butter and drizzle with the lime juice. Sprinkle the spiced salt over the corn and serve at once.
The aromatic cooking liquid can be refrigerated overnight. The spice mixture can be stored in a jar for up to 2 days.
Chaat masala is a spice blend that can be found at Indian and Middle Eastern markets.