Step 1

Start by heating a large pan 10" or larger over medium heat. While it heats prepare the onions by dicing them 1/2" or cutting them into half moon slices.

Step 2

Add the oil to the heated pan along with the sliced onions, and cook over medium or medium-low until the onions become softened and browned, about 20-30 minutes. Season to taste with sea salt and set the onions aside. You will have about 1 cup of caramelized onions.

Step 3

Preheat the grill or griddle over medium heat until it reaches a steady temperature of 350-400ºF. While the grill heats prepare the burger ingredients and mix together your choice of secret sauce recipes.

Step 4

For the burgers, divide the yellow mustard equally between the 4 patties, about 1/2 teaspoon per patty and spread it in a thin layer over one side of the burgers. You want to grill the mustard side down first.

Step 5

Grill the burgers for 6-10 minutes per side depending on desired doneness, adding the optional cheese slices halfway through the cooking time when you flip the burgers.

Step 6

When the burgers are done to your liking, serve them right away with all the toppings and secret sauce.