Veggie Burgers

• 8 wheat buns (whole)
• 3 lentils (cooked)
• 3 egg whites
• 240 ml mayonnaise (light)
• 110 gr cheddar cheese
• 110 gr bread crumbs (plain)
• 65 gr carrots
• 60 gr green onion (chopped)
• 30 ml catsup
• 32 gr spinach (fresh)