Make burgers: In a small bowl mix together kosher salt, paprika, onion powder, garlic powder and a few turns of cracked black pepper. Add ground beef to a large bowl and 2-3 tsp of the seasoning mixture. Mix together until it is incorporated but be careful not to over mix or it may result in a tough burger. Divide evenly into (6) 1-inch-thick burger patties. Indent the center of each one with your thumb. Sprinkle the remaining seasoning on top of the burger patties evenly on each side.

Caramelize onions: In a medium saute pan melt oil and butter on medium-low heat. Add the onions and a sprinkle of kosher salt. Stir together and caramelize onions until medium to deep golden brown, about 20 minutes, stirring occasionally. Stir in brown sugar and whiskey and light with a long-handled lighter or skewer to burn off the alcohol. Cook for another 2-3 minutes, stirring together until most of the liquid has evaporated. 

Make aioli: In a small bowl whisk together olive oil, mayonnaise, lemon juice, Worcestershire sauce, and garlic until combined. 

Cook burgers: Heat a large cast-iron skillet on medium-high heat. Add the vegetable oil. Cook patties for 3-4 minutes on each side for a medium center and an internal temperature of 160-165 degrees F. Allow burgers to rest for 2 minutes or so.

Assemble burgers: Spread 1 tbsp of garlic aioli between the two buns, a handful of arugula, a burger patty, 1-2 tbsp of whiskey onions and top with crumbled blue cheese.