Bring a large pot of water to a boil and salt it.

Add rice and cook, adjusting heat to maintain a steady boil.

Stir occasionally.

When rice is nearly done, about 10 minutes later, drain it.

While rice cooks, heat 2 tablespoons butter over medium heat in a wide skillet or casserole, preferably nonstick.

Arrange potatoes in butter.

Pour cooked rice over potatoes.

Turn heat to very low.

Add 2 tablespoons butter and cover.

Cook over lowest possible heat, undisturbed, for at least 1 1/2 hours, or until potatoes are crisp (use a spatula to peek).

Keep the dish on minimum heat for another half hour, or turn off heat and reheat over medium-low heat for 15 minutes before serving.

During last few minutes of cooking, add black pepper and, if you like, 2 more tablespoons of butter.

Cut potato-rice cake into pieces and serve.