Like the barbecue and fried chicken waves before it, Chicago is now having a ramen moment.

Ramen fans have been packing into River North’s Ramen-san the past few weeks – and at 90 seats, it’s a behemoth by traditional standards. They offer three types of ramen here, but they’re most proud of the tonkotsu, which is made by boiling pork bones for hours.

“The best thing I learned is everything opposite of what I used to do. So we’d start off with a French stock and it would be nice, simmering, something like that; the tonkotsu, you’re boiling it the whole time to get all the fat and everything to emulsify,” said Doug Psaltis, the chef at Ramen-san. “That’s the heart and soul.”

Psaltis first adds a scoop of miso, then the broth and a tangle of boiled noodles imported from New York. Crunchy bamboo, soft seaweed and a soft-boiled egg are typical; chashu pork amplifies the pork broth, and garnishes include scallions and pickled ginger. There’s also a deep, dark shiitake mushroom version for vegetarians, arriving with cubes of firm tofu.