50 gram patties where made from a equal mix of shin, hanger, and chuck steak.  50 grams (1.7 ounces) was a bit too big, I found.

Clockwise from bottom: hanger, shin, chuck

50 grams is about 1.7 ounces.  I'd make them a bit smaller next time.

They were pressed into a flat top at about 320 degrees.  You're not looking for a high-heat sear here.  You're actually looking to steam the patty.  So keep the heat low.  But press them down hard and flat.  You want these to be thin, and they will puff up a bit while cooking.  And no, pressing down on cold beef doesn't magically push all of the fat solids out of it, so smash away.

Salt and pepper (if desired) the patties.

Thinly sliced onions (I used a mandolin) are then immediately pressed into the patties.  Don't be shy with the onions.  They are a main component of the flavor profile of the slider, and add the moisture you'll need to steam the patty and buns. 

The patty cooks on one side for about 1 minute or so, and then they are flipped over.  Now the onions are on the flat top, under the burger.  

Right after the flip you cheese the patty. Use some crappy American cheese for this.  That's the flavor you want, and it melts quickly.  But don't smash them down on this side.  The cheese will stick to your spatula, and you will be forcing liquid out, since the meat and onions are now warm.

Place the top bun on top of the cheese (or the patties, if no cheese used), and the bottom bun on top of the top bun.  The onions and burger are really going to steam the whole mess. 

Look at that steam!

After another minute or so, your slider is done.  Use a spatula to pick the mess off the flat top, take the bottom bun and slide the meat/onions/top bun onto it. 

Condiments? I am a fan of ketchup and sliced pickles on a slider.  Fairway in Paramus has some great sliced pickles in the big barrels, and of course there are plenty of good pickles out there.  The acidity and crunch of the pickles is a nice contrast to the wet, soft sandwich.  

For the bun, and let's face it, this thing has a lot of bun, we used Martin's potato rolls and Pepperidge Farms slider buns.  These are both a decent size for sliders, although I'd prefer something a bit smaller.  Pepperidge farms buns were a bit too dry and quite unexceptional.  In our taste taste with the sliders, the Martin's won.  They are slightly larger, but much more airy.  Additionally, you can gut them to pull out some of the dough.  This is preferable.

Here's a comparison of slider buns (left is Pepperidge Farms, right is Martin's):

You can see the Martin's weighs a bit more than the Pepperidge Farm.

But it's also taller, and more airy.  So, you can easily gut the Martin's bun to make it effectively smaller and lighter than the Pepperidge Farm.  Gutting the Pepperidge Farm's dense doughy bun is next to impossible.

They are about the same diameter, although the Pepperidge Farm is a bit smaller. 

Our preference was a gutted Martin's roll. 

It would be fairly easy to bang out a bunch of these for a party.  There's a bit of prep work (patties, onions, gutting the buns) which can be done well in advance, but if you have something like the Lodge cast iron griddle that I used, you can easily cook 10 at once.  And all of those burgers and onions in one small space will help the steaming process.  A long spatula works well to pull several off at once, and then you're on to your next batch as your guests "oooh" and "ahhh."

Important points:

• A patty smaller than 1.7 ounces makes it easier to double up for a double slider, and makes for a better single slider.  I'm going with about 1.4 ounces next time.
• More onions is a good thing.
• Don't be skimpy with the American cheese.
• Pickles are good.
• Gut your Martin's buns.
• Low heat, not high.
• The show featuring the New Jersey Sliders from White Manna and White Mana is called Food Feuds, not Food Wars.