Espresso and Lime

Make the caramelized onions...
0 Place a large skillet over medium heat and add a tablespoon of olive oil 
2 Add the thinly sliced onions and season with a tablespoon of granulated sugar and a generous pinch of salt and black pepper 
3 Cook, stirring occasionally, for about 30 minutes or until the onions are soft and deeply golden brown. Add a splash of stock if the skillet becomes dry (reduce the heat, if necessary)
4 Add a tablespoon of balsamic vinegar, cook for another 5 minutes and then transfer the caramelized onions off of the heat
Make the burgers...
6 In a large bowl, combine 16 ounces of beef with 2 cloves of finely minced garlic, 2 tablespoons of dried onion flakes, 1 teaspoon of onion powder, 1 teaspoon of garlic powder, 1 tablespoon of Worcestershire sauce and a generous pinch of salt and black pepper 
7 Divide the mixture into 4 equal portions 
8 Form each portion into patties 
9 Place a large skillet over medium to medium high heat and once the skillet is warm, place the patties down leaving space in between each 
10 Cook for 2-3 minutes or until the underside is crisp and golden brown
11 Flip the patties and cook to your desired level of doneness 
Assemble the burgers...
13 Turn the heat off, but leave the skillet on the burner 
14 Top each burger with caramelized onions and shredded Gruyère 
15 Cover the skillet for about 60 seconds to allow the Gruyère to melt
16 Transfer the burgers onto brioche buns garnished with mayonnaise and lettuce