Both work for this recipe. Just make sure that the raw shrimp are deveined and thawed before cooking. Unless you're buying shrimp off the boat fresh, the shrimp you buy thawed at the seafood counter have most likely already been frozen and thawed. Keeping frozen shrimp on hand allows you to whip this easy recipe up whenever you want. Cooks note: you can use pre-cooked shrimp for this recipe. Follow the recipe exactly, only decreasing the time the shrimp are cooking in the butter to not overcook the shrimp. However, we feel starting with raw shrimp deepens the overall flavor of this dish.