Melt butter in heavy large saucepan over medium-high heat. Add corn and onion. Saute until onion is golden, about 10 min. Add 5 cups water,milk, 1t coarse salt, and 1t pepper to pan; bring to boil. Gradually add grits, whisking until mixture is smooth and comes to boil. Reduce heat to low and simmer until grits are thick and tender, whisking often, about 15 min. Mix in cheese and chipotle chile. Stir until cheese melts.