Make the chicken patties.  

1.   Preheat the oven to 300°F. Prepare a  sheet pan lined with parchment paper and a sheet pan lined with a wire rack.
2.   In a large mixing bowl, add the ground chicken and sprinkle the salt, garlic powder, smoked paprika, and pepper over the chicken. Mix the spices into the chicken and add the beaten egg and mix until well combined. 
3.   Divide the chicken mixture into 5 even parts and shape into ¾-inch thick patties, roughly the size of your buns. 
4.   In a wide shallow bowl, add the Panko breadcrumbs and coat the chicken patties with crumbs. Place the crusted chicken patties on a sheet pan and put in the fridge for 30 minutes.  

Make the sauce.  

1.   In a small bowl, add the mayo, cornichons, ketchup, sriracha, garlic powder, and salt. Mix well and set aside.  

Cook the chicken patties. 

1.   In a large nonstick frying pan, heat 1 cup of olive oil over medium to medium-high heat for  2 minutes. Add two or three chicken patties and shallow fry for 3 minutes until deeply golden and crispy. Flip the patties. Continue frying for 3 more minutes until deeply golden and crispy. Remove the patties from the pan and place on the rack-lined baking sheet. Top the patties with a slice of cheddar cheese and keep cooking in the oven for 10 minutes or until cooked through. Repeat with the remaining chicken patties.  

To Assemble your burgers. 

1.   Toast your buns until golden brown. 
2.   Take your bottom bun and spread a tablespoon of the sauce and top with one or two lettuce leaves (don’t forget to salt them!). Put the chicken patty on top and spread another tablespoon of the sauce. Add a few sliced tomatoes and as many marinated onions as you’d like. Close with the top bun and repeat with the remaining burgers. 
3.   Serve right away and enjoy!