1. divide the meat into 4 equal portions and roll in balls
2. season with salt and pepper.
3. heat the oil in the pan or griddle over high heat until the oil begins to shimmer.
4. cook the burgers, smashing down with a spatula about 4 minutes
5. flip over the burgers.
6. cook beef burgers until golden brown and slightly charred on the second side
7. add the cheese, if using, to the tops of the burgers during the last minute of to melt the cheese.
8. place the burgers on the bun bottoms and, if desired, top with tomato, lettuce, onion, and a dollop of horseradish mustard mayonnaise.
9. pile on the potato chips, top with the bun tops, and serve immediately.

horseradish mustard mayonnaise:

1. whisk together the mayonnaise, mustard, and horseradish in a small bowl and season with salt and pepper. cover and let sit to allow the flavors to meld.
2. the sauce can be prepared 1 day in advance and kept covered in the refrigerator.