Mark your calendars, cheeseburger lovers. September 18th is National Cheeseburger Day, and we’re celebrating big at Serious Pie Ballard. Chef ET is taking over the patio flattop with his dream smashburger. @mishimareserve beef, brown butter onions, American cheese, and red eye ketchup on a bun from @rachels.bagels.and.burritos. Join us 11:30am-6pm for this one-day pop up. To pre-order: Choose September 18th as your pick-up date, and then select your cheeseburger!