Melt the butter in a heavy medium skillet over medium heat. Season the shrimp with salt and pepper, to taste. Cook for about 4 minutes until almost fully cooked. Using a slotted spoon, transfer the shrimp to a plate and tent it with foil. Add the onion and garlic and cook until the onion is translucent, about 6 minutes. Stir in the wine and bring to boil, scraping up the brown bits on the bottom of the pan. Boil for 1 minute. Stir in the lime juice and parsley. Return the shrimp to the pan and toss to coat with sauce and Continue to cook until the shrimp are fully cooked, about 1 minutes. Season with salt and pepper, to taste. Transfer the shrimp to a serving platter and serve alone or with white rice, if desired.