1. In a heavy 8- to 10-inch skillet, heat the butter over moderate heat. When the foam subsides, add the scallions and onions, and cook them, stirring frequently, for 5 minutes, or until the onions are soft and transparent but not brown.
2. Add the tomatoes and cook, stirring, for 5 minutes. Add the cream, coriander, oregano, cumin, salt and a few grindings of pepper, and, stirring constantly, drop in the cheese.
3. Cook, stirring, until the cheese melts. Traditionally, "chorreada" sauce is served over boiled potatoes (or cooked string beans) and often accompanies sobrebarriga.
