BBQ Chicken Burgers - The Weary Chef

Ingredients

• 1 pound ground chicken
• 1/2 sweet onion finely diced
• 1/2 cup barbecue sauce
• 1/2 cup cheddar cheese shredded
• 1 egg
• 1/2 teaspoon kosher salt
• 1 cup bread crumbs or crushed cornflakes
• 4 slices cheddar cheese optional
• 4 hamburger buns
• reduced-fat mayonnaise
• 2 tomatoes sliced
• 2 cups baby spinach leaves or lettuce