1. 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.
2. 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.