A grilled burger is thick and juicy, and might be pink in the center.
A smashed burger is thin with caramelized beef and crispy edges. The juiciness comes from the cheese, onions, and burger sauce.
Make the burger sauce.
Mix together 1/2 cup mayo (Duke's preferred if you can find it) with 2 Tbsp Worcestershire sauce and as much fresh black pepper as you like.
Cook patties for about 1 1/2 minutes and then flip.
Add cheese to half the patties (or all of them, if you prefer).
Add caramelized onions to half the patties and stack two together.
Spread both buns with a little of the sauce.
Place bacon on the bottom bun and top with your burger stack.
You can add more condiments if you want, but you don't need to.
To make your burger taste more like a "fast food burger," wrap in foil and let steam for 2-3 minutes before serving.
This softens and warms the buns and marries the whole burger together.