This Italian dish was originally made, I understand, from small, lobsterlike shellfish called scampi, langostinos or prawns. In America it is often made with shrimp. Either shrimp or langostinos will do if you've got plenty of fresh garlic.
Behead, shuck, and devein the shrimp, leaving the tails on. Heat the butter and olive oil in a large skillet. Sauté the green onion and garlic for 4 or 5 minutes. Add the lemon juice, salt, and pepper. Cook, stirring as you go, until the mix starts to bubble. Add the shrimp. Cook for about 5 minutes, depend on the size of the shrimp. Add the lemon zest and parsley. Stir. Serve hot with lemon wedges, hot garlic bread, rice, and vegetables.