How to Make It
In a large skillet, melt the butter with the shallots over low heat. Season the shrimp with salt and arrange them in the skillet in one layer. Cook over very low heat for 10 minutes. Turn the shrimp, sprinkle with the parsley and cook until pink and curled and just white throughout, 8 to 10 minutes longer; you’re essentially butter-poaching the shrimp. Transfer the shrimp to a plate.
Add the wine to the skillet and simmer until the sauce is slightly thickened, about 1 minute. Stir in the watercress and season with salt. Toss just until wilted. Transfer the watercress to a platter and top with the shrimp and any pan juices.