Whisk the Mayonnaise (1/2 cup), Ketchup (1 tablespoon), Gochujang (1 tablespoon), Dill Pickle Relish (2 tablespoon), Garlic Powder (1 tablespoon), Onion Powder (1/4 teaspoon), Chipotle Chili Powder (1/4 teaspoon), Salt (1/4 teaspoon), and Ground Black Pepper (1/4 teaspoon) in a bowl, cover with a cling wrap and refrigerate for 1-2 hours.
In a large bowl, combine the Lean Ground Beef (1 pound), Onion Powder (1 tablespoon), Garlic Powder (1 tablespoon), Paprika (1 tablespoon), Ground Black Pepper (1 tablespoon), Dried Oregano (1 tablespoon), Salt (1 teaspoon), Ground Cumin (1 tablespoon), Red Chili Powder (1 teaspoon), and Gochujang (1 tablespoon) and mix well using your hands.
Divide the beef into four equal portions and shape them into patties. Make sure the patties have a larger diameter than the buns because they possibly might shrink while cooking.
Place a thumb in the center of each patty, making a small dent which will reduce the risk of shrinking. Chill for 30 minutes in the refrigerator.
Fill a cast-iron or a deep pan with Olive Oil (to taste) and bring the heat up to medium-high.
In another bowl, combine the Whole Wheat Flour (1 1/2 cup), Chipotle Chili Powder (1/2 teaspoon), Salt (1/2 teaspoon), and Ground Black Pepper (1/2 teaspoon) to make the crispy onions.
Pour the Buttermilk (1 cup) into a separate bowl and start dunking the Yellow Onion (1/2) in the buttermilk, then generously coat with the dry ingredients mixture.
Work in batches and fry for 1-2 minutes until crispy. Drain excess oil by laying on a paper towel or cooling rack.
Cut the Brioche Hamburger Bun (4) in half and toast on a skillet at medium-high heat and set aside.
Melt Butter (1 tablespoon) on the skillet and when it’s melted, drop in a patty and cook for 4 minutes per side until edges look brown and crispy.
After flipping once, cook the other side for 3 minutes, add Mild Yellow Cheddar (4 slice), and cover. Leave it for one minute so it totals to 4 minutes on each side.
Add Arugula (1 cup) in a small bowl and drizzle some Olive Oil (to taste). Season lightly with salt and pepper.
Spread sauce on both buns, place arugula, followed by the patty, and finally top it with crispy onions. Devour this delicious meal, you earned it!