Mix the water, cornmeal, salt, and olive oil, if using. Put the bowl, uncovered, in the microwave, and set the microwave for 5 minutes on HIGH.
Halfway through cooking, take the polenta out of the microwave and stir thoroughly. Add a drizzle of milk, if desired. Put the bowl back in the microwave and finish the cooking time. Check at 5 minutes; it should be getting rather thick. (It will thicken even more as it cools.)
Eat with a little more milk, plus brown sugar and walnuts — or topped with a poached egg.
