My favorite grilled cheese is my mom's, made casually -- even distractedly -- while on the way out the door or whiling away a weekend afternoon. I am inexplicably unable to recreate them on my own, despite their extraordinary simplicity.
She makes them using bread from a round, crusty Hy-Vee loaf (usually leftover from the night or nights before) slathered in margarine (margarine!) and 1 1/2 or so slices of Kraft American singles.
Having meltable (which, yes, typically means highly processed) cheese is key to a good grilled cheese sammy. Another reason I like my ma's is because they are unpredictably shaped. Slices from a round loaf can be ginormous ovals or misshapen nubs.
Since I only get the real deal once or twice a year these days, I have to substitute with random, inferior fixes. *Sigh.* I haven't found any that quite do it for me yet. Where do you get your grilled cheese fix around these parts?