Make the beef patties: Place the ground beef in a food processor. Combine the salt, pepper and onion powder, then add in two or three parts while pulsing the ground beef into a fine grind
Cover a half baking sheet with parchment paper. Using your hands and/or a rolling pin spread the beef over the parchment paper and into a large 9″ x 12″ square
Divide the beef into 12 patties with a table knife. Don’t cut the parchment paper
Make (5) 1/4″ holes in each patty using a wooden dowel or any blunt round object. Pattern the holes like the 5 pips on a pair of dice
Place the baking sheet in the freezer and freeze the patties solid about 90 minutes
While waiting for the patties to freeze, re-hydrate the onions with a mixture of the water and beef stock. Bring it to a low simmer while stirring, turn off the heat, cover and steep until the burger patties are ready
Heat a griddle to 250 F. Remove the patties from the freezer, turn over and peel off the parchment paper and separate the patties carefully to avoid breaking them. stack them and return to freezer until ready to cook
Separate and carefully slice the rolls into tops and bottoms with a bread knife
When the griddle is hot, spread the onions with plenty of water over the surface large enough to place all the patties in rows on the onions. Let the patties touch and make sure you place the patties ON the onions, not on a bare griddle surface
Cover the beef patties with the inside of the bun bottoms, then cover the cracks between the bun bottoms with the bun tops to trap the steam
Cook for 5-6 minutes until done. Use a spatula to scoop up each burger with some onion, place the top under the spatula and slide it off. Turn over and set aside. Repeat for the remaining burgers
Lift the top of each burger and add cheese (optional), then a pickle or two and optional condiments, then replace the top bun