Heat the oven to 350°F. Grease a 3-qt. nonstick ovenproof skillet; pour in the cornmeal, water, milk , butter, and salt and stir with a fork until blended. The mixture will separate and take more than half the cooking time to come together. Bake uncovered for 40 minutes. Stir the polenta, taste, add salt if needed, and bake for another 10 minutes. Remove from the oven and let the polenta rest in the pan for 5 minutes before pouring it into a buttered bowl to scoop out and serve or onto a wooden board or pizza peel to slice into wedges.
