Q: My hamburgers always puff up on the grill. Should I be mashing them down with a spatula the way fast food chefs do?A: Whatever you do, don't try to flatten the burger with a spatula -- you'll only succeed in pushing out the juice and you'll have a dried-out burger on your hands. Your burger puffs because ground beef contains collagen, the animal's connective tissue, which is ground up along with the meat. As the meat cooks, the collagen contracts. When it contracts around the edge, it acts like a belt and pulls the edges in, forcing the top and bottom up and down.
The solution is in the way you form the patties. First of all, be careful to treat the meat gently. Take about a 6-ounce portion and shape it by tossing it back and forth between your hands. This brings the meat together without overworking it. Make it about 3/4-inch thick and 4 1/2-inches across. Now here's the trick. Put it on a flat surface and press the center of it with your fingertips until you have a well about 1/4-inch deep. When you cook the patty, the well will swell to level the surface and your toppings will not fall off.
-Food Network Kitchens
