1 1/3 pounds ground American lamb
Kosher salt and freshly ground pepper
Vegetable oil, for greasing the grill
4 ounces American blue cheese, such as Point Reyes Blue, Rogue Creamery Oregon Blue, or Maytag Blue, cut into 4 slices or crumbled
4 hamburger buns, preferably whole wheat, brioche, or pretzel buns
1 large heirloom tomato, such as Beefsteak, Brandywine, or Cherokee Purple, cut into 4 thick slices
4 butter lettuce leaves
1/4 cup pickled red onions
Optional Condiments: mayonnaise, ketchup, whole grain mustard, pickles
Prepare a hot fire in a charcoal or gas grill.
In a large bowl, mix the lamb with a few big pinches of salt and several grinds of pepper, tossing gently with the tines of a fork; be careful not to mash the meat. Divide the mixture into 4 portions and form hamburger patties, pressing gently to shape.
Grease the grill grates with oil. Place the burgers on the hottest part of the grill and cook, turning once, until a nice crust forms on each side and they are medium-rare to medium in the middle, 7 to 10 minutes. Move the burgers to a cooler part of the grill as needed to avoid blackening or flare-ups. Transfer the burgers to a platter and immediately top with the blue cheese.
Meanwhile, grill the buns, cut side down, until toasted, about 1 minute. Place a hamburger in each bun.
Arrange the tomato slices, lettuce leaves, pickled onions, and any additional condiments on a large serving tray. Serve the burgers and toppings at the table, and let everyone assemble their own perfect lamburger.