Mix up that meat, bread crumbs, egg, soup mix, water, and seasoning
Lay the mixture out on some parchment paper and roll it out super thin. You can portion it out for 3" squares or for as many buns/rolls as you bought. I ripped a piece from the large ball, made a small ball, and flattened onto a roughly 3" square of burger paper.
Castle pokes holes in the meat, so if you're true to style - poke some holes in the squares using a straw or something. I used the ass-end of a chop stick.
I fired up the Blackstone to medium/medium-high and laid out the onions. Let them start cooking and dropped on the grub. (If you've had a castle/krystal - steam is king - so get those buns on there to soften up!)
After the steam got to 'em, I scooped 'em up - onions and all - and flipped. Add the bottom bun to the flipped burger and steam that one up too. When it's done - put it together and you got yourself an onion bomb of a burger!