In a large, heavy saucepan, bring the water to a boil. Add the salt, then gradually whisk in the cornmeal. Reduce the heat to low and cook, stirring often, until the mixture thickens and the cornmeal is tender, about 15 minutes. Remove from the heat and stir in the butter. Coat an 11×7″ baking dish with 1 tsp. of oil. Transfer the hot polenta to the prepared baking dish, spreading evenly to 3/4″ thick. Cover and refrigerate until cold and firm, about 2 hours. Preheat the oven to 250. Cut the polenta into 2×1″ pieces. In a large, heavy skillet, heat the remaining olive oil over a medium-high flame. Working in batches, fry the polenta pieces until golden brown on all sides, about 3 minutes per side. Using tongs, transfer the polenta pieces to paper towels and drain. Place the polenta pieces on a baking sheet and keep warm in the oven while cooking the remaining batches. Transfer the polenta pieces to a serving platter. Sprinkle with Parmesan cheese and salt, and serve, with marinara sauce alongside.