Divide the chopped romaine lettuce between two large bowls. Top the lettuce with the cherry tomatoes, red onion, pickles, and avocado. Set these aside so they are ready for the hot chicken.
In a medium mixing bowl, gently combine the ground chicken with salt, pepper, garlic powder, and onion powder. Do not overwork the meat, as this can make the burgers tough. Form the mixture into four loosely packed balls.
In a small ramekin, stir together the mayonnaise, yellow mustard, pickle juice, and smoked paprika until smooth. This creates a low-carb version of a classic “special sauce.”
Heat the olive oil in a large cast-iron skillet or non-stick pan over medium-high heat. Place the chicken balls in the pan. Use a sturdy spatula (and a piece of parchment paper to prevent sticking) to press the chicken down firmly until it is very thin. Sear for 3-4 minutes until a dark golden crust forms, then flip and cook for another 2-3 minutes until fully cooked through.
Place two smashed chicken patties into each prepared bowl. Drizzle the burger sauce over the meat and vegetables. Serve immediately while the chicken is hot and crispy.