Place collards, onion and salt pork in a large saucepan. Cover with water and cook over medium heat, until greens are tender (about 15 to 20 minutes). Drain, discard pork, reserve the greens and onions and set aside.

Spray a nonstick skillet with cooking spray. Heat skillet over medium high heat and add egg whites. Season with salt and pepper to taste and saute all together, stirring constantly until done to taste.

Meanwhile, spray another nonstick skillet with cooking spray and heat over medium high heat. Saute Canadian bacon on both sides until lightly browned. Remove from skillet and drain on paper towels.

To Assemble Stacks: Place bread slices on a broiler pan. Top each with 1 slice Canadian bacon and equal portions greens, egg whites and cheese. Broil until cheese bubbles and melts. Sprinkle chives on top and serve.