1Melt butter in a large skillet over medium-high heat. Stir in the olive oil. Sauté onion, parsley, garlic, and white pepper in hot butter mixture, stirring continually, until onion is tender, about 3 minutes.
Add shrimp to onion mixture. Cook over high heat, stirring frequently, until shrimp turn pink and mixture is hot and bubbly, about 3 to 5 minutes.
Add sherry and lemon juice to the shrimp mixture and mix well.
Cook over medium heat, stirring frequently, until sauce is thickened, about 8 to 10 minutes. Serve over rice, if desired. Garnish with parsley and lemon slices, if desired.