Spray 3 ramekins with cooking spray. Then mix together in a separate bowl the egg whites, salt, black pepper, parsley, and chives. Mix with a whisk for 1 minute until the egg whites begin to froth a little.
Place a teaspoon of finely chopped spinach in each of the ramekins. Then divide the egg white evenly among the 3 ramekins. Top with additional spinach and 3 sliced grape tomatoes. Sprinkle 1 teaspoon of tomato basil feta over each of the ramekins. Bake for 20 minutes until done and egg whites have risen.