Chiles rellenos are stuffed with everything from cheese in the north of Mexico to crab or seafood along the Gulf Coast. Though chiles rellenos are usually fried, they are baked in this vegetarian version. Bell peppers can be substituted for the poblano chiles.
Remove stem ends of poblano chiles, leaving chiles whole; discard seeds and membranes. Set aside.
Place tomatoes, onions, and garlic on a foil-lined jelly-roll pan. Bake at 500° for 30 minutes (garlic should be lightly browned; remove before 30 minutes, if necessary). Let vegetables cool 10 minutes. Peel tomatoes and garlic; discard skins. Remove cores from tomatoes. Place tomatoes, garlic, onion, and chipotle chile in a food processor, and process until smooth. Strain through a sieve into a large saucepan; discard solids. Add water, oregano, and bay leaf to pan; bring to a boil. Reduce heat, and simmer, uncovered, 40 minutes or until reduced to 2 cups. Remove from heat; discard oregano and bay leaf. Add 1/4 teaspoon salt and dash of pepper to tomato mixture; set sauce aside, and keep warm.
Combine corn and next 6 ingredients (corn through dash of pepper) in a bowl; stir well. Pack 3/4 cup corn mixture into each poblano chile. Place stuffed chiles on foil-lined jelly-roll pan. Bake at 500° for 20 minutes or until chiles are blackened, turning after 10 minutes; peel chiles.
Spoon 1/2 cup tomato sauce onto each of 4 plates, and top with stuffed chiles. Garnish with whole chives and cilantro sprigs, if desired.