The bun
Soft potato rolls are the default for smash burgers. Motz and Kenji both name Martin’s potato rolls.
From: Classic Smashburger “All the Way”, Classic Diner-Style Smashed Cheeseburger, Oklahoma Fried Onion BurgerSeeded white buns suit thicker burgers (Motz, Weissman).
From: Thick Pub Classic Burger, Joshua’s Perfect Burger
Always toast it
Butter the cut sides and toast them on the griddle until golden (Weissman, the Shake Shack cookbook).
From: Joshua’s Perfect Burger, ShackBurgerKenji toasts his buttered buns under the broiler for about a minute.
From: Classic Diner-Style Smashed Cheeseburger
The sauces
ShackSauce: mayonnaise, Dijon, ketchup, a little pickle brine and a pinch of cayenne.
From: ShackBurgerAnimal-style sauce: mayo and ketchup with deeply caramelized onion and diced pickle (Weissman).
From: Animal Style BurgerWeissman’s everyday burger sauce: ketchup, mustard, mayo and Worcestershire.
From: Lacy Edge Smash Burger
Every tip above is taken from the recipe it links to. Where the experts disagree, we say so rather than picking one.