Burger Queen for a Day

On Monday*, I made what was most likely the best burger I've ever made.  What troubles me about this--aside from the fact that from now on, everything  is downhill--is I'm not at all sure why it was that good.
  1. I don't usually buy ground meat from Key Food unless it's for something that's going to be cooked well done.  This time, I had no time, told myself I was being silly in the first place, and bought a 1 pound package of ground chuck, making for burgers at around 1/2 pound each.  Bigger than that is kinda revolting, not to mention hard to handle; smaller can be way too easy to overcook.
  2.  I'd been doing a lot of cooking lately on a nonstick grill pan.  Love it, but it doesn't quite deliver the char you want surrounding that rare, beefy-red interior.  Since I also wanted to fry some onions for topping the burgers, I used a  well-aged cast-iron skillet, which retained a bit of the oniony flavor to pass on to the patties.
  3.   Used a splash of Worcestershire along with salt and pepper, nothing else.  I also remembered to add the crucial dent, using my knuckles, on top, so that patties wouldn't puff up.
  4.  Placed them on the searing hot pan, making no attempt to turn them until they released from the surface.  Too soon, and they will leave their crusty goodness on the pan.  I've done that once too often.
  5.  The cheese, ah yes, my most frequent downfall.  I love cheeseburgers.  I love them so much that I've tried every which way to make them work.  The usual way, that is, throwing on the cheese at the last minute, either resulted in half-melted cheese or overcooked burgers.  I spent a year or two messing around with other methods, like stuffing the cheese inside the burger, a la Minnesota's Juicy Lucy.  It didn't work for me: the cheese either leaked out, making an unholy sticky mess on the pan or I didn't use enough cheese, suffusing the burger with a vaguely cheesy flavor and oleaginous feel.  Too much cheese?  A blistered mouth.
  The solution was so obvious that I'm almost embarrassed to mention it.  A minute or so before the burgers are done, slap the cheese on, the cover with a pot lid or metal bowl. Perfectly melted cheese every time.    I've used aged cheddar, blue, provolone, pepper jack, and quite a few others but I  always come back to Kraft slices.  So sue me.
  6. English muffins? Okay, but a bit coy and brunchy.  Standard-issue burger buns?  Pap.  My answer is the wondrous Big Marty's sesame roll.  Sturdy enough to hold up to burger juice, cheese, and onions, coated with so many sesame seeds you can barely see the bun.  Roll royalty.  Toasted on the inside only, using my toaster, the world's slowest, on the bagel setting.

  What did the trick: One, some or all of the above?  Or, was it, as the ineffable Irma said, a kismetburger?  I won't know until I try again, which should be sometime soon.

*Not this past Monday, or even this past part Monday.  Started writing this about a week ago. Lousy fall cold left me disinterested in food and life in general.