Heat a large skillet or griddle over medium. Butter the cut sides of the buns and toast until golden, 1–2 minutes. Set aside.
Divide the beef into 8 loose balls (about 3 oz each). Season the tops with salt and black pepper.
Raise heat to medium-high and add the oil. Working in two batches, place 4 beef balls on the hot surface. Top each with a square of parchment and press firmly with a spatula to ¼-inch thick. Cook 1½ - 2 minutes until the edges are well browned and crisp. If using, brush a little mustard on top, then flip. Add a slice of cheese to each patty and cook 30–45 seconds more until cheese melts. (Cook to 160°F if you prefer well-done.) Stack two patties for each burger.
Add the greens from the Fresh Express® Farmhouse Ranch Chopped Kit to a large bowl, drizzle with the dressing from the kit, and toss to lightly coat. Sprinkle with the crunchy toppings.
Build the burgers by placing a double patty stack on each bottom bun. Top with a generous handful of the prepared salad and cap with the top bun.
Divide the remaining prepared salad among plates to serve as a side.