His wife Michelle is on vacation in Spain – but President Barack Obama still had some A-list company as he celebrated his 49th birthday on Wednesday.

Obama paid a visit to one of his hometown's best restaurants, Graham Elliot in Chicago, with a guest list that included Oprah Winfrey, Gayle King, senior adviser Valerie Jarrett and longtime pals Eric Whittaker and Marty Nesbitt.

"We were humbled and honored that the president decided to join us for dinner on such a special occasion," chef Graham Elliot tells PEOPLE. "The [restaurant] team is super-psyched we have such a foodie sitting in the White House."

Elliot, whose restaurant bills itself as Chicago's first "bistronomic" eatery that prepares updated classic American dishes, was only a little stressed about his high-profile clients – because he'd been in Los Angeles doing PR for his new FOX show, Master Chef, on which he is a judge.

"My flight was actually held up due to Air Force One landing at O'Hare, so we were racing to the restaurant to head him off," says Elliot

But the dinner was a success, and after the meal Obama visited the kitchen to thank the staff for the food.

On Thursday morning, the president was back to work, appearing at the Ford Motor Company plant in Chicago, where he told workers, "It is good to be back in Chicago. It's good to see some friendly faces, be back in the old neighborhoods."

When one member of the audience shouted "Happy Birthday" to the president, he responded, "Thank you. I’ve gotten a little more gray hair since I was last down here. But it is wonderful to be back home."