Burger Haven isn't a pop-up, but a restaurant within a restaurant. During the lunch hours, the back part of Haven Gastropub in Oldtown Pasadena turns into Burger Haven, serving burgers, fries, and milkshakes. There are 6-7 items on the menu including the Haven burger, the lamb burger, a veggie option, and Here's the Kicker topped with habanero, serrano, jalapeno, and pickled ghost chili! I tried a bite of this and was dying from the spiciness, but I know quite a few people who would love it! You can see the full menu here.
For my lunch, I went instead with the Shake and Bake, which is their fried chicken sandwich. It's made with Mary's free range chicken, coated in corn flakes and pan fried, topped with rosemary mashed potatoes, gravy, braised collard greens, and honey mustard on jalapeno-habanero bun ($9)
Regardless of how full I was after that fried chicken sandwich, there's always still room for a Nutella shake ($5)!