A sturdy, dark sear is an important and fundamental aspect of a good cheeseburger. A proper sear provides a shift in texture with crunch, chewiness, and a gradient of doneness, which goes from Well-Done to Rare. This also provides a range of flavors as one bites through that range of cooking temps. Keep in mind that a little carbon goes a long way, so it is not necessary to blacken the burgers with char.
The brown colors developed in the sear are the result of the Maillard Reaction. More can be read about that here. It is important to note that the Maillard Reaction/browning, only occurs at temperatures above 310 degrees Fahrenheit.
It is possible to deliver a good sear on a grill and this is generally accomplished by using a hot-burning hardwood rather than gas as a heat source. The hardwood provides both convective heat from the flames and radiant heat from the embers, which is more consistent than the convective heat delivered by a gas burner. The heat rising from the gas flames travels around the patty, and only the heat stored in the grill surface is directly applied to the patty at a sufficient temperature. This is why burgers cooked on a gas grill tend to have grill marks rather than an even sear. Tessaro’s in Pittsburg does and exemplary job with a grill, and they use a hardwood heat source.
|A Griddled Sear on an Umami Burger|
Regardless of the cooking method, burgers should be turned once during the cooking process, and, like steaks, they should be allowed to rest for a few minutes prior to consuming them. Cheese is best applied while the burger is cooking to insure that it melts evenly and really binds to the surface of the burger.