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.