Separate the meat into 4-ounce portions and roll each portion into a ball, like cookie dough. Gently pat the balls into patties 1/4 inch thick; you want to flatten the patties without beating up the meat. Stack the patties on large baking sheets. Cover the baking sheets with plastic wrap and refrigerate until it's time to grill.
Fire up a charcoal grill following the instructions in Cooking with Charcoal (page 8), or fire up a gas grill to high heat with the lid closed to help it get nice and hot. While the grill heats, get all your burger fixings ready: cheese, tomatoes, lettuce, pickles, avocados, and sauce. Set them up on a station near your grill along with bowls of salt and pepper.
Brush the cut sides of the buns lightly with butter. Put the buns cut side down on the grill to toast them lightly. Transfer the toasted buns to a big roasting pan or disposable aluminum pan. Tent with foil to keep the buns warm while you grill the patties. (You could also toast the buns in the spaces between the patties while you grill the patties.)
Place the burger patties on the grill, seasoning them lightly on both sides with salt and pepper as you go. Cook the patties for 2 minutes. Turn the patties and put a slice of cheese on each one. Close the grill if it has a lid, and cook the patties for another 2 minutes until they're done.
To dress the burgers, coat the toasted sides of the buns with sauce. Layer the burger like this: bottom bun, 1 lettuce leaf, 4 pickle chips, 2 patties, 1 tomato slice, and enough slices to equal one-quarter of an avocado. Spoon a little more sauce over the avocado and close the burger. Wrap the burger in paper, if you have it. Stack the burgers on a platter, no higher than two burgers, and put them out on the buffet for the crowds to dig in.