Extremely hard layer after cooking the burger on the grill

You did everything right except you overcooked your burgers. Those are relatively thin patties, they won't take 7 minutes a side on high heat, that is what caused that hard crust. I'd be cooking them 3 minutes a side at most.

A small thing but I'd suggest you replace olive oil with corn, sunflower or another high temperature oil. Olive oil will smoke at a high temperature and add off flavors. This had nothing to do with your thick crust.

There was some more of the same minced meat. I did a few trials yesterday to try the comments here. I used both iron grill and granite pan. And in my experiment with a granite pan, I was able to observe the reason better.

First of all, I did not apply any olive oil to the patties. When I put the hamburger patty in the pan that I had preheated, a serious oil accumulation occurred under the meatball. And with the effect of this oil, I actually seemed to be frying. I baked each side of the hamburger patties for 3 minutes. And the result was almost like 7 minutes in the pictures. After all, my observations were as follows;

1- Minced meat was much more fatty than it should be.

2- 3-4 minutes is ideal for a thin burger like mine.(It will be medium well or well done)

3- Since we make hamburgers in the pan, the oil of ground beef causing frying because it remains in the pan again. If it were made on the barbecue, all the oil would flow down.

4- The ground beef we buy will be fatty for better taste but not as much as mine. In my researches, it was called 20%, which is ideal for fat content. I think my mince was around 50 percent.

Thanks everyone.

Don't put them in the oven. There's no baking supposed to be going on. You're pan-frying the meat.

Heat the grill pan to moderately hot. You'll want to see grill marks in the finished patties.

You're not making meatballs here. Do not put a ball in the grill pan and smash it down into a patty.

You'll want to avoid handling the patties as much as possible to avoid making them tough. Grab a handful of ground meat and gently flatten it out in your hands.

Making the center slightly (.25 in./a few mm) thinner than the periphery will keep the patties from swelling up in the middle.

Don't add any oil. If you use an 80/20% or 85/15% grind, that's a lot of fat to begin with. A higher fat content is not recommended. You could add a pat of butter--mostly for flavor.

You can season the patties before you cook them, but the "usual" way is to add salt/pepper in the pan while the opposite side cooks.

Gently place the patties in the pan and cook over medium-high to high heat for about three or four minutes. Flip the patties over and cook for about 3 more minutes.

That's all. No baking, no oven, no broiling. Just pan-fry on each side for around 3 minutes. The grill ridges on the pan should elevate the meat enough while it's cooking to drain off most of the fat, but you want a little bit to remain for flavor/moisture, etc.

For absolute optimal results use an outdoor grill (barbeque) with good charcoal. Pan-frying is only a "second-best" option.

Here is a very comprehensive tutorial: How To Make Burgers on the Stovetop Check out the pictures for details on making the patty, the color (fat content) of the ground meat, etc.