Combine ground chicken, spinach, cheddar, breadcrumbs, onion, garlic, mustard, Worcestershire sauce, salt, and pepper until well mixed.
Form the mixture into 4 equal patties, pressing lightly to hold shape.
Heat olive oil in skillet and sear patties 5–6 minutes per side or until internal temperature reaches 165°F (75°C).
Let the patties rest for 3–5 minutes to retain juices.
Toast burger buns, add toppings like lettuce, tomato, or extra cheddar, and serve warm.
