Provel cheese

Provel is a white processed cheese prominent in St. Louis cuisine. A combination of cheddar, Swiss, and provolone, Provel has a low melting point and a gooey texture and buttery flavor. Provel cheese is the traditional topping for St. Louis–style pizza. It is also used in pasta sauces, cheese soup, salads, and sandwiches such as the Gerber sandwich. Provel is rarely used or sold outside of St. Louis. Provel can be purchased at St. Louis-area grocery stores such as Schnucks or Dierbergs Markets, and Hy-Vee grocery stores across the Midwest.

Source: Wikipedia