I was at Whole Foods yesterday and they were sampling their beef/bacon blend of ground beef. It was delicious. Maybe not as good as Man pax but I don't have a grinder to do my own. Not cheap but it's Whole Foods.

The perfect burger requires a high quality beef patty. You don't want to mix anything into the beef patty because that changes the chemistry of the meat which requires you to mess with the cooking.

Your better cuts of beef will make a better beef burger. It's okay to use NY Strip or Filet Mignon and have it ground at the butcher shop. Make it into 1/3 pound patties and put a divot in the middle so it doesn't plump up round while grilling. Salt and pepper only and allow the patties to sit out on the counter for 30 minutes while the grill heats. High heat open flame, charred to medium rare. Fire is good. Never squeeze or squish the patty. Let it char in fire on each side for 2-3 minutes only flipping once then remove and allow to sit a few minutes under foil as it continues to cook through.

Grill the buns.

Everything else is left up to you.

IMO filet mignon is way too lean and even most NY strip is as well. I also cook the burgers straight from the fridge. I found that when I brought them close to room temp first they would be too well done when I got a good char. I like mine rare. I do allow to sit after they are cooked though.

I was only suggesting the two beef cuts as an example of what you can use. For me beef chuck at 20% fat is good. And by the way, I rely on Alton Brown are a lot of my cooking strategies. And trial and error. :-)

What is your preferred beef cut?

Chuck is good. I think my favorite blend is brisket and short ribs but since I don't do my own grinding I am at the mercy of the butcher for that. They usually require a large quantity to do it. Sirloin adds a good beefy flavor to a mix too. I really liked the flavor the bacon gave to the burger I tried at whole foods. ..I might have to buy some and try at home.