In a large mixing bowl, combine ground chicken, chopped spinach, shredded cheddar, breadcrumbs, onion, garlic, mustard, Worcestershire sauce, salt, and pepper. Mix gently until fully incorporated.

Divide the mixture into four equal portions and shape into patties about ¾ inch thick.

Heat a skillet over medium heat and add olive oil. Once hot, place the patties in the skillet without overcrowding.

Cook patties for 5-6 minutes on one side until golden brown. Flip and cook for another 5-6 minutes until the internal temperature reaches 165°F.

Remove patties from skillet and rest for approximately 3 minutes.

Assemble the burgers by placing a patty on the bottom bun, adding desired toppings, and finishing with the top bun.