1. Pat scallops dry and sprinkle with pepper and 1/4 teaspoon salt.
2. Heat oil in a 12-inch heavy skillet over moderately high heat until hot but not smoking, then cook scallops, turning over once, until browned well and just cooked through, 5 to 7 minutes total. Transfer to a platter and loosely cover.
3. Heat 2 tablespoons butter in skillet over moderately high heat until foam subsides, then saute mushrooms, stirring occasionally, until golden, about 4 minutes. Add shallots and garlic and saute, stirring, 2 minutes. Add Sherry, vinegar, soy sauce, and remaining 1/4 teaspoon salt and simmer, uncovered, stirring occasionally, 2 minutes. Cut remaining 2 tablespoons butter into small pieces.
4. Remove skillet from heat and stir in butter until incorporated. Spoon sauce over scallops.

Yield: 4 servings