What makes a pizza “St. Louis style”? Well, it can’t be a pizza, by the conventional definition. It’s not just that the toppings are distributed right up to the saucy edge. Or that it uses yeast-free dough, which results in a cracker-thin, unusually crisp crust. Without Provel cheese, every other notable characteristic wouldn’t amount to the pizza that St. Louisans think of as their own. And Provel, legally-speaking, isn’t even cheese.

Many of the St. Louisans who grew up with Provel love it; for others, it’s an acquired taste. Texturally, Provel is close to processed American cheese, and added liquid smoke gives it a tangy aftertaste reminiscent of Gouda. Despite being a fan, a well-known comedian called it “melted plastic from the ’80s.” Another reviewer said it’s like “chewing on a candle that’s lit at the other end” with “the texture and sheen of wax.”

But Provel has been the city’s topping of choice since it was invented by St. Louisans in the mid-20th century. The plastic package reads “Pasteurized Process Cheddar, Swiss, and Provolone Cheese,” but the stuff inside looks more like a twisted wad of freshly-extruded udon noodles than a block of cheese. Nevertheless, its low melting point, and gooey, buttery texture work perfectly on the pie it was designed to grace. Biting or slicing into the creamy stuff, even when cooled, never causes the sort of elastic cheese-pulling disaster that can casually strip half a pizza of its rapidly-hardening mozzarella.

For those who have a hard time accepting pizza they don’t understand, consider this theory: Perhaps St. Louis–style pizza, with its crisp crust, fake cheese, and hefty supply of toppings is actually more similar to nachos than pizza. With a little change in expectation, by the time you pull that second gooey, square-shaped slice from its box, the technicalities of traditional pizza might be the furthest thing from your mind.