Step 1

Gently stir together beef, 1/4 cup blue cheese, salt, black pepper, and worcestershire sauce just until incorporated.

Step 2

Shape into 4 thin patties, and refrigerate.

Step 3

Heat a cast iron skillet until hot over medium heat. Add the butter (or oil) to a large cast iron skillet, and add the onions.

Step 4

Stir well, breaking up the onions and coating the onions in the butter.

Step 5

Cook for 10 minutes. Stir and reduce heat to medium-low. Cook for another 25-35 minutes, stirring every 5-10 minutes, until golden brown. Remove the onions from the skillet and set aside.

Step 6

Add the oil to the skillet and turn the heat to medium-high. Place the burgers in the hot skillet and cook for about 3-5 minutes until the burger easily releases.

Step 7

Flip the burger and reduce heat to medium. Cook until the burger reaches desired doneness. (Note: I cooked mine about 5-8 minutes for a medium/medium-well burger)

Step 8

Remove from heat and let rest a few minutes before serving

Step 9

Serve each burger with about 1 tablespoon blue cheese, 1/4 cup onions and 1/4 cup arugula with or without a hamburger bun. Enjoy!