Add 8 cups water, the oil and salt to a large saucepan over medium-high heat and bring to a boil.
Slowly stream in the polenta while whisking constantly. Reduce the heat to low and cook until the polenta is thickened and smooth, about 3 minutes.
Meanwhile, place a large, heavy-bottomed pan over medium heat. Drizzle with olive oil and evenly coat the bottom of the pan. Sprinkle 1 cup of the Parmesan evenly over the bottom of the pan and allow to toast until golden brown and nutty, about 2 minutes. Remove from the heat.
Pour the polenta over the Parmesan crust and smooth the surface. Sprinkle with the remaining 1/2 cup Parmesan. Set at room temperature until firm, 20 to 30 minutes. (At this point, the polenta can be refrigerated up to overnight.)
When ready to serve, place the pan back over medium heat to warm the cheese. Place a large plate or serving platter over the surface and invert the polenta onto the plate. Serve topped with your favorite sauce.