Hunan beef is a Chinese-American restaurant dish, typically made by stir-frying beef with mixed vegetables and soy sauce. The culinary tradition of Hunan Province, which makes extensive use of fresh and pickled chilies, is typically referenced only by adding bell peppers or chile peppers to the dish.
For a discussion of authentic Hunan beef and an attempt to simulate Hunan dry-smoked beef in Western kitchens, see this Woks of Life article on Hunan Beef
For more on Hunan cuisine and Hunan chiles, see Hunan cuisine and duò jiāo (pickled chile peppers).