This epic onion burger recipe features 2-2 oz smashed patties smothered in caramelized onion cheese, pickled red onions, onion jam, and caramelized onion mustard all nestled onto red leaf lettuce in a toasted onion roll. More onions per square inch than any other burger! (probably)
Stir for a couple of minutes, then add salt, pepper, the onion soup mix, water, and instant coffee.
Give it another stir, bring it up to a boil, put on the lid, and simmer over medium heat for 10 minutes.
After 10 minutes, remove the lid and stir in the brown sugar, vinegar, and Worcestershire sauce. Cook over medium-low until most of the liquid has evaporated out and the mixture is jammy.
Taste and add a touch more salt if necessary.
Cool, then cover and store in the fridge for up to 2 weeks.
For the Pickled Red Onions
Pack the siced onions pretty tightly into a jar or other glass container.
Place water, vinegar, sugar and salt in a pan, and bring to a boil.
Boil for 10 seconds or so, making sure all the sugar has dissolved.
Pour over the onions to submerge (you may have extra brine).
Cool, cover and chill.
Store in the fridge for up to 2 weeks.
For the Patties
Evenly mix all the patty ingredients except for the salt and pepper.
Form into 8 balls about 2 oz each.
Cover and refrigerate until ready to cook (up to 2 days).
Time to Make The Burgers!
Grab the lettuce, buns, mustard, onion jam, pickled onions, cheese, and burger mix. Also grab a little butter or bacon fat from the fridge.
Slice the buns horizontally. Spread the cut sides with a little melted butter or bacon fat, and broil until golden brown. Don't toast, because you don't want them crisp on both sides, just the cut sides.
Spread about 2 Tablespoons onion jam on the bottom buns.
Spread about 2 Tablespoons caramelized onion mustard on the top buns.
Place 2 leaves of lettuce on top of the bacon jam. That's where you'll put your burger patties once cooked.
Heat your skillet or griddle over medium-high heat.
Place 2 balls of burger mix in the pan, several inches apart.
Smash them down firmly all around to flatten. Further thin out the edges with the edge of your spatula for maximum crispy-edged goodness.
Cook about 1 1/2 minutes on 1 side.
Salt the patty before scraping up and flipping.
Once flipped, add a piece of cheese on top of each patty, then cover the pan with a lid.
Cook for about 1 minute, covered.
Scrape 1 patty and surrounding "cheese skirt" up and place on the lettuce.
Top with a healthy amount of pickled onions and then add the second burger on top.
Top with the mustard-covered top bun.
Repeat until all 4 burgers are done.
Devour while patties are hot.
Notes
Feel free to make these as "regular" 4 oz burgers. In that case, form into patties about 4 1/2" across, and cook for about 5 minutes on 1 side and 3-4 on the other. Top with 1 or 2 slices of cheese and melt with the lid on or just place the patty directly on the bun. There's no real wrong way!Other substitutions: use your favorite mustard in place of the onion mustard. Spread with bacon jam or even pepper jelly as opposed to onion jam.Use brioche buns, potato rolls, Kaiser rolls, etc if you cannot find onion rolls.No matter how you make them, enjoy every bite!You can also cook the burger patties, cool and refrigerate to reheat within 2-3 days. Then you can go all-out with the toppings as written, or do your own thing!