For the sauce: Process all ingredients in blender until smooth, about 2 minutes, scraping down sides of blender jar as needed.
For the shrimp: Sprinkle shrimp with ½ teaspoon salt and ¼ teaspoon pepper; set aside.
Heat oil in 12-inch nonstick skillet over medium heat until shimmering.
Add onion and ½ teaspoon salt and cook until softened, about 5 minutes.
Add garlic and cook until fragrant, about 1 minute.
Add wine and bring to boil. Cook until reduced by half, about 4 minutes.
Add shrimp and cook, stirring occasionally, until opaque and just cooked through, about 4 minutes.
Stir in butter and sauce and cook until butter is melted and sauce is heated through, about 1 minute.
Season with salt and pepper to taste. Sprinkle with parsley and serve.