Heat olive oil in a skillet over medium heat; cook and stir kale, mushrooms, salt, and pepper until until mushrooms are tender, 5 to 10 minutes.
Whisk eggs, egg whites, and milk together in a bowl until frothy.
Spray a non-stick skillet with cooking spray and place over medium heat; cook and stir egg mixture until cooked through, about 5 minutes. Transfer eggs to a plate and top with string cheese and kale mixture. Garnish eggs with Sriracha and parsley.