Copycat In N Out Double Double Burger, Animal Style

1 1/2 onions, diced
oil or butter

The Secret Sauce

water
4 hamburger buns
16 oz. ground chuck, 80% lean
16 slices American cheese, sliced, whole milk (I used Boar's Head from the grocery deli)
oil
yellow mustard
4 lettuce leaves
16 pickle slices

Secret Sauce
5 Tbsp. + 1 tsp. mayo

2 Tbsp. ketchup
2 Tbsp. dill pickles, minced
2 tsp. yellow mustard

Carmelizing the onions, beginning stages

Cook the onions in a little oil or butter in a pan, over medium heat. Let them brown a little, then add a little water to the pan to reliquify the juices. Let the water cook down and let the onions brown a little more. Repeat this process with the browning and water for at least an hour; it could even be an hour and a half. Don't rush this process. Cook until the onions are a real deep brown color, where they're falling apart and spreadable, like a jam. Onion jam.

Preheat oven to 400 F.

Burgers with mustard, cooking

Lay your hamburger buns, open, on an ungreased cookie sheet, and toast for 2 minutes.

To make the sauce: Mix all ingredients together in a small bowl, then set aside.

 Split your ground chuck into 8 equal 2 oz. pieces, and flatten. Cook in a tiny bit of oil on one side, while adding a large dollop of yellow mustard to the uncooked side. Flip when ready, then cook until cooked through, or however you like your burgers cooked.

Lay a single slice of cheese on each meat patty right before the meat is done cooking, so the cheese is melty.

Assembling

To assemble: Spread a good amount of the sauce on the bottom bun. Add 4 pickle slices on top of the sauce. Add the lettuce leaf. Then layer one patty with cheese. Spread a tablespoon or two of the onions on top. Then add another patty with cheese. Top with the top bun. Enjoy this ooey gooey goodness. One of the best burgers I've ever had.

Ooey Gooey Goodness

Makes 4 Double Double burgers.