Three things do most of the work:
- Open flame cooking. Fat renders and drips onto the flame, which sends smoke back onto the patty.
- Thicker patties on the Angus line. A thicker patty can take the hotter, faster cook without drying out.
- Cooked to order. Burgers are built after you order rather than held, which is why the wait is slightly longer than at some competitors.
That last point is worth setting expectations around. During a lunch rush, a Thickburger takes longer than a value cheeseburger because it needs more time over the flame. If speed matters more than size, order down the menu.
Portion size is the main lever if you're thinking about calories rather than just cost. The Angus patty is the reason a Thickburger is more filling than a standard cheeseburger, but it's also the reason it carries more calories before a single topping is added. Bacon, extra cheese, and mayo-based sauces stack on top of that fairly quickly, so a Original Thickburger with mustard and pickles sits well below a Bacon Cheese Thickburger with all the usual add-ons, even though both start from the same patty.