1. Bring milk to a boil with 2 cups water in a medium saucepan and add a large pinch of salt. Adjust heat so liquid simmers. Add cornmeal in a steady stream, whisking as you do to prevent lumps. When it has all been added, let mixture return to a boil, then turn heat to low. Polenta should be just barely simmering.
2. Cook, stirring occasionally and being sure to scrape sides and bottom of pan, for 15 to 20 minutes, until mixture is creamy and cornmeal tastes cooked. If mixture becomes too thick, whisk in some water, about 1/2 cup at a time. (I added about 2/3 cup water in 1/3 cup increments.)
3. Taste and season polenta as necessary with salt and pepper. Take pan off stove, stir in the butter or oil and the cheese if you are using it, and serve, passing more cheese at the table if you like.

Serve with sautéed greens and a fried egg for a simple simple dinner.