A two-level fire is the best way to cook a thick burger.
What this allows you to do is cook over high heat to get
the sear you need (if the coals or flames start to flare up, just
cover the grill with the lid until the flames subside) and grill
over lower heat to gently cook the burger through.
Conventional cooking wisdom, as we know, tells us that
you should sear first and finish on the cool side. But! This
methodology is all based on the false premise that searing
first helps lock in juices, something which we now know to
be a fallacy. In fact, after running a few side-by-side tests, I
found that doing the exact opposite results in more evenly
cooked meat: Start your burgers on the cool side of the grill,
using a thermometer to check for doneness, and then
transfer them over to the hot side once they’re within 10
degrees of your desired final serving temperature. By doing
this, you warm the meat to the point that a deep, well-
charred crust can develop over the high heat in about half
the time it would take for it to do so if you slapped the
burger on there raw. Minimizing time spent over high heat
maximizes even cooking, resulting in a better, tastier burger.