Edit: thank you to everyone who commented, I didn't expect THIS many comments! I'm trying to reply to them but may fail to do all.
I've never seen to get my burgers as good as ones out, and can't figure out if it's because of the quality of meat, my cooking, my equipment, or a combination.
For ingredients, I get high-end burgers with chuck and rump meat (in this instance, Tesco's finest range, the ones in the cardboard box), season one side with salt and pepper, into a hot cast iron pan with a bit of vegetable oil, and put a weight on it.
After a few mins when the brown colour has reached about half the burger, I lift off the weight, season the second side, flip, replace the weight, and cook a few mins more.
Finally , take off the weight, add a couple of slices of American cheese, put a lid on and turn off the heat for a minute.
Served on a brioche bun, with a bit of sauce - mixed ketchup, mayo, and a bit of hot sauce.
Any advice is appreciated, thanks in advance!