I actually don't have them often because they are such a PIA. And only in Summer when the butter is soft enough to spread easily. But, in the summer who wants a hot sandwich??
My Mom always buttered one side of the bread and then, holding it precariously on her fingertips, built the other side - spread mayo or peanut butter or whatever while not getting the butter on her and then put it in the pan and then did the other slice the same way and topped it. Cooked one side, flipped cooked the other. Big mess.
Then I saw the first 15 minutes of the first episode of Girl Meets Farm.
She put the butter in the pan and melted it. And then put bread on top of the butter and 'toasted it', THEN she took the bread out of the pan, toasted side up, built her sandwich easy peasy - no balancing on fingers, no butter everywhere - spread what you want, add what you want, then put one toasted side on top of the other and back into the pan to do the other sides.
It make so much sense and make grilled sandwiches so easy! I've had about one or more a week since I made this discovery. Thankgod I didn't die first.
I'm guessing, if only by the nonchalant way she did this, that she did not invent the technique. Probably everyone in the world, except my mother (and her mother) has made grilled sandwiches this same way for centuries.
But, now I'm a member of your club and I'm delighted.