Heat a grill pan over medium-high heat until lightly smoking. Oil the pan and saute the onions with a pinch of salt until browned, about 4 minutes. Turn the heat to medium and cover the onions to steam for an additional 2 minutes. Remove from the heat.
Roll two 4-ounce balls of meat and flatten into patties. Sprinkle with salt and garlic powder and brush with mustard. Flip the patties and repeat.
Turn the heat back to medium-high and when slightly smoking, coat with olive oil. Grill the patties until browned, about 1 1/2 minutes per side. Meanwhile, toast the roll on the unused side of the pan for about 2 minutes. Lay 2 pickles on top of the patties and cover each with a slice of cheese. Cover the patties melt the cheese.
Spread ketchup on the top of the roll. On the bottom of the roll, stack both patties and top with potato chips.