I had been hearing about the sack of White Castle hamburgers for years so about 6 years ago I came across some frozen one's at Sam's. I bought them since I'm almost always willing to try new foods.
If I remember correctly there were a couple of different ways they could be heated up with one being in the oven. Now, I knew frozen one's wouldn't be as good as fresh one's so I decided not to use the microwave (didn't want the bun to get hard) and used the alternative method of heating them up in the oven.
Even making allowances for frozen never being as good as fresh those were some of the nastiest tasting things I'd ever put in my mouth. If I was faced and forced into a choice between boiled okra and White Castle hamburgers I'd be hardpressed to choose which one I'd take. As a point of reference, even looking at boiled okra engages my gag reflex!
Are the frozen White Castles anywhere near like the fresh one's? If so I probably won't ever sample the real thing. Blech!!!
Not just no, but hell no!
I've never had a real slider in person, either--but I can tolerate the frozen cheeseburger ones the same way I tolerate McD's Happy Meal cheeseburgers--as appetizers. Cut into quarters, one little tidbit to pop in your mouth, seasoned however you want to.
But I wanted to tell you, after seeing your sigline that you have the very best onion burgers within somewhat of a not too long driving distance from you, if the place is still there.
J&W Grill in Chickasha -- the BEST you ever tasted, if you like grilled onions.