Because of the close ties to such a central holiday, the camote is very important to the culture of the Mexican people. Camotes are pressure-cooked sweet potatoes served individually to each customer. Traditionally the camote is a pressure-cooked sweet potato topped with condensed milk, and seasoned with chili peppers, cinnamon, or strawberry jam. Camotes vendors are distinctive because of the very noisy, high-pitched whistle created by the cart they cook the potatoes in. One can walk down the Streets of Mexico City and know where a camote vendor was located blocks away. Even though this is a traditional Mexican street food the camote is mostly only located in or around Mexico City or other metropolises. Additional foods There are other street foods made with tortillas. Tostadas are flat hard tortillas either fried or dried on which are placed a variety of toppings such as shredded chicken, pork, beef, seafood, cheese and salsa. Quesadillas are derived from the Spanish word for cheese, queso, and refer to a tortilla folded in half and filled with cheese and possibly other ingredients such as spicy meat, mushrooms, chili pepper strips and more. The type of cheese used generally varies by region and in some areas, cheese is not even used unless requested. Empalmes are three stacked corn tortillas with beans, some kind of meat or stew which are typical in the state of Nuevo León. Known as "sincronizadas", the Spanish word for synchronized, are two corn tortillas with a meat and cheese filling then toasted on each side until the cheese melts. "Gringas", as the slang word for people with lighter skin tones, are similar to quesadillas or sincronizadas but made with flour tortilla, hence the name. Tlayudas are large dried tortillas topped with beans and other ingredients similar to a pizza or large tostada popular in the state of Oaxaca. There are street foods that use the same corn dough used to make tortillas, but in different preparations. Gorditas can be found in almost all parts of the country. They are very thick corn dough patties fried in oil or cooked on a comal (a traditional griddle). After cooking, they are split and filled with a variety of ingredients. There is a flour dough version of this in Coahuila. Bocoles are small round gorditas popular in Hidalgo, Tamaulipas, Veracruz and San Luis Potosí. After cooking they are split and filled with ingredients such