JW Burger Sauce: 

1. Begin by preheating a small saucepan over medium heat.
2. Once hot add the butter to the pan and let it melt. Once the butter has melted add the diced onion and season lightly with salt.
3. Allow the onions to cook, stirring often, until they are caramelized and deep brown in color, about 20-25 minutes. If the onions begin cooking too fast or getting too much color, add in 2 Tbsp water and stir to combine. Let the water evaporate and then continue caramelizing the onions. Once caramelized, remove from heat and allow the onions to cool completely. 
4. In a medium bowl, add in all the ingredients besides the onions and stir until combined.
5. When the onions have cooled, stir them into the sauce and serve immediately or keep in an airtight container in the fridge for up to 5 days. 

‍Burger:

1. Heat a large griddle or 12” (30cm) cast iron pan over medium heat. 
2. Evenly spread the softened butter on the inside of both the top and bottom bun, about 1.5 tsp per bun. Repeat with the rest of the buns. 
3. Toast the buns, butter-side down, moving them around the surface of the griddle until evenly toasted and golden brown, 2-3 minutes. Turn the buns over and toast the outside of the top and bottom buns just slightly, about 30 seconds. Repeat with all your buns and set aside. 
4. Wipe out the same griddle or pan with a paper towel and increase the heat to medium high. Once your cooking surface is hot, add two 2 oz meat balls to the pan, making sure they are at least 4” (10cm) apart. Pinch a handful of onions into your hand and fold them up into a ball. Add that to the top of one of the meat balls and then use a heavy spatula or burger press to smash the onion and meat ball into the griddle until it is ⅛” (3mm) thick. Repeat with the second patty and then season both with salt and pepper to taste. Cook the burgers for about 1 minute and 30 seconds, or until you have a deep golden brown crust underneath. Using a thin, sturdy spatula, or an edge scraper, scrape aggressively underneath the burger and flip, being careful to keep them in the same place so they continue cooking in their own fat.  
5. Add one slice of American cheese to each burger patty. Optionally, add a lid or turned over metal bowl to speed up the melting process. Cook for another 1 minute or so until the cheese is melted and the burger is caramelized on the second side. 
6. Place one burger patty on top of the other and set aside in a warm area. Repeat with the rest of your beef, making a total of 4 double stacked burgers. 
7. To assemble, spread the sauce on both your top and bottom buns. On each bottom bun add three slices of pickle shingled over each other. Add your double patties to each burger followed by the top bun. Serve immediately.