The best-cooked hamburger patties begin with lean, grass-fed ground beef. When you shape hamburger into patties, press the meat together loosely -- a tightly-packed burger can be tough and rubbery. Make average-sized patties a uniform 3/4-inch thickness and the approximate diameter of the bun. Prepare the patties for cooking by placing a 1/4-inch-deep thumbprint depression in the center of each one to keep them from swelling during cooking. Once the burgers come off the heat, use an instant-read thermometer to make sure they register a safe internal temperature of 160 degrees Fahrenheit, as recommended by the U.S. Department of Agriculture.
Preheat a cast-iron skillet to medium-high before adding the patties so the meat sears quickly, sealing the juices inside. To sear, brown the patties on one side, then turn them and brown the other. Place the skillet with the flipped burgers into a preheated 350 F oven to finish cooking, about five minutes.
Form lean ground beef into 1/3- to 1/2-pound patties. Smaller patties tend to become leathery in the oven. Bake the patties on a wire rack in a pan with shallow sides -- a jelly roll pan will do -- in a 200 F oven for about 20 minutes, or until an instant-read thermometer says 120 F in the center of each burger. Make a foil tent over the burgers while you heat a small amount of cooking oil in a skillet. The internal temperature continues to rise while the patties are under the foil. A quick sear for about 45 to 90 seconds on each side browns the patties and seals in the juices. Check the final internal temperature after searing to ensure the meat reached the recommended 160 F safe temperature.
Broiling is similar to grilling in that both methods use radiant heat to cook the meat. Brush a light coating of oil on the broiler rack, then place patties on the rack. When the tops of the patties are brown and juices collect in the indentation, flip the patties. Return them to the broiler for 3 to 5 minutes. Remove the burgers from the heat and tent them with aluminum foil for five minutes, checking the temperature in the center of the patties.
Preheat the grill and place the patties on the rack in the hottest part of the grill. Watch the meat, and when juices begin to collect in the thumbprint indentation, about 4 to 5 minutes in, flip the burgers. Cook them for about 2 to 4 more minutes then remove them from the grill. Tent them with foil and check the internal temperature before serving.