In a 4-quart saucepan, place cool water over high heat and bring water to a boil. Season with salt and pepper. Add polenta in a thin stream, whisking constantly. When all polenta is in, pull pot to front of burner, remove whisk, and start stirring with a wooden spoon. As polenta thickens, add poppy seeds and cheese and remove from heat. Stir cheese through and serve immediately with oxtails.