• Add burger ingredients to a large bowl then blend using your hands just until mixed.
• Score the burger mixture into 4 sections, then form the patties and transfer to a parchment paper or wax paper lined baking sheet.
• Cover with plastic wrap and refrigerate 15-20 minutes. This helps the patties hold together when grilled.
• Peel and thinly slice the onions using a sharp knife or mandoline.
• Add butter and olive oil to a hot skillet over medium heat then add the onions, season with salt and pepper and saute 10-12 minutes or until softened and golden brown.

Grilling the Burgers:

• Remove burgers from the fridge. Using a paper towel, dab any excess moisture from them then lightly brush with olive oil on top side only and lightly season with salt and pepper.
• Preheat the grill to medium-high heat (about 450 degrees). Oil the grates using cooking spray OR grill tongs and a rag with a generous amount of oil. NOTE: it’s really important to oil the grates well so the burgers don’t stick.
• Add burgers to the hot grill oiled side down. Cook 3-4 minutes or until seared and the meat easily releases from the grill grates without sticking.
• Turn the burgers over and continue grilling another 3-4 minutes or until the burgers are cooked through to an internal temperature of 160 degrees on an instant-read thermometer (they’ll continue to cook as they rest).
• While the burgers are still on the grill, divide caramelized onions between them then top with pepper jack cheese (the melted cheese holds the onions intact!). Grill 1-2 minutes letting the cheese melt then remove from the grill. 

  Place buttered buns on the grill grates for 2-3 minutes.

Assembling the burgers:

• Add shredded lettuce and tomato slices to the bottom bun. Top with a burger patty. Slather the top bun with chipotle mayo then place on top of the burger. Eat right away.