Wash 2 to 3 pounds fresh spinach leaves in several changes of water, removing yellowed or damaged leaves. Drain thoroughly. Put leaves in a thick-bottomed saucepan with 4 tablespoons butter, and salt and freshly ground black pepper, to taste. Simmer gently, stirring constantly, until spinach is soft and tender. The mass of crisp leaves will begin to “dissolve” almost at the first contact with the heat, and there will be just enough to serve 4 to 6 new spinach fanciers.