Preheat oven to 350°F. Generously butter a 9x13” or 3-quart baking dish. Freeze for 10 minutes.
Bring 3 cups of water and 1 teaspoon sea salt to a boil in a large heavy saucepan over medium-high heat. Gradually whisk in grits and return to a boil. Reduce heat to medium-low and cook, whisking often for 12-15 minutes until thickened. Whisk in milk and cook, stirring constantly for 5-7 minutes or until grits are creamy.
Remove from heat. Stir in corn, next 7 ingredients, and remaining salt. Spread mixture in the prepared dish. Place on a parchment-lined baking sheet.
Bake at 350°F for 50 minutes or until puffed, firm around the edges, and slightly soft in the center. Remove from oven to a wire rack and cool for 5 minutes before serving