1. Preheat oven to 350°. Generously butter a 3-qt. baking dish; freeze 10 minutes.
2. Meanwhile, bring 3 cups water and 1 tsp. salt to a boil in a large saucepan over medium-high heat. Gradually whisk in grits; return to a boil. Reduce heat to medium-low, and cook, whisking often, 2 to 3 minutes or until thickened. Whisk in milk, and cook, stirring constantly, 3 to 4 minutes or until grits are creamy.
3. Remove from heat, and stir in corn, next 7 ingredients, and remaining 3 tsp. salt. Spread mixture in prepared dish. Place on an aluminum foil-lined jelly-roll pan.
4. Bake at 350° for 50 minutes or until puffed, firm around edges, and slightly soft in center. Remove from oven to a wire rack, and cool 5 minutes before serving.