In a large heavy skillet, heat the butter and olive oil over low heat. Add the garlic, red pepper flakes, salt and black pepper and cook about 4 minutes, stirring occasionally, until the garlic is tender but not browned.
Increase heat to medium and add shrimp and sautué, turning the shrimp once with tongs, until shrimp are just cooked through, about 2 minutes each side.
Add the parsley and cook for another 2 minutes. Using tongs, remove the shrimp from the pan, pour the sauce over the shrimp, garnish with parsley, and serve immediately.