In a 10 to 12-inch non-stick pan, heat 2 tablespoons olive oil until smoking.
Place scallops in and do not move them. Allow them to cook until crisp and golden brown, unmoved for 5 to 6 minutes. In a 12 to 14-inch saute pan, heat remaining oil until smoking over high heat.
Add shallots and saute until softened, about 3 to 4 minutes.
Add mushrooms and toss 3 to 4 minutes until softened.
Add vinegar and then frisee. Toss quickly, season with salt and pepper and divide among 4 plates. Without turning the scallops, remove and arrange 3 on each salad.