There’s a new Chicago-style pizza mash-up in town, but it contains a rather unexpected ingredient (for pizza, at least): mustard.

As part of its “Chi-Town Flavors” series, iconic Chicago deep dish brand Giordano’s teamed up with Jim’s famous Maxwell Street Polish to create a “Jim’s Original Deep Dish Pizza,” according to a press release. The pie is layered with Jim’s Polish sausage, caramelized onions, nearly a pound of gooey Wisconsin mozzarella cheese for Giordano’s iconic “cheese pull,” and a “touch of mustard in the sauce.”

According to the release, the pizza, which brings together the two famed institutions, is now available frozen and can be shipped nationwide, exclusively from ship.giordanos.com.

“Jim’s Original has always been about tradition, family, and authentic Chicago flavor,” Jim Christopolous, owner of Jim’s Original said in the release. “Partnering with Giordano’s is a natural fit. Together we’re honoring the city’s food history while creating something new that fans everywhere can enjoy.”

The 10-inch pizzas come in packs of two, four and six, the release said. The collaboration follows Giordano’s other “Chi-Town Flavors” mash-ups, including Giordano’s x Buona Italian Beef Deep Dish Pizza.

Earlier this year, two other famed Chicago brands — Portillo’s and Lou Malnati’s — debuted a “Chicago Dog Deep Dish Pizza.”