A burger bun is a soft, mildly sweet, yeast-leavened bread roll -- usually round and slightly flattened -- used to hold a burger patty and its toppings. It's typically made from wheat flour, water, yeast, sugar, and fat, giving it a pillowy interior and a lightly crisp crust; its neutral flavor makes it a blank canvas for fillings from grilled meats to pickled vegetables and sharp cheeses. Bakeries mass-produce them for the fast-food industry, though home bakers also make enriched versions with added butter, garlic, or herbs.