As he wrapped up a brunch shift at the Australian cafe Two Hands in the Little Italy section of Manhattan, Christopher Mortenson saw his phone light up. All afternoon, he had been waiting for the notification: ABC Cocina, an upscale Latin American restaurant in the Flatiron district, needed a line cook. He had an hour to get there.

When the shift ended, Mr. Mortenson started sprinting uptown. On his way to the restaurant, he ducked into a supply store to pick up a white chef’s jacket, which he threw over his T-shirt. He arrived at ABC Cocina just before 5 and spent the evening charring peppers with a blowtorch and stuffing pork into pillowy tortillas.

In December, Mr. Mortenson , tired of working 50 hours a week for low pay, quit his job as a cook at a vegetarian restaurant in Manhattan and became a full-time member of the gig economy. Now he races around New York, working shifts at a rotating cast of restaurants that use the hospitality staffing app Pared. So far, he has cooked in more than 70 kitchens, including Osteria Morini in SoHo and Riverpark in Kips Bay.

“I have to turn the notifications off at night — I can’t sleep,” said Mr. Mortenson, 51, who has worked full time at restaurants in Las Vegas, San Francisco and Austin, Tex. “They send me so many jobs I can’t even look at my app right now without 10 jobs being on there.”