Preheat the oven to 425 degrees F. Lightly spray a medium-sized oven-safe skillet with olive oil spray. Put all 6 egg whites in one bowl and the three yolks in another. Whisk the whites for at least 2 minutes to aerate them. Set the skillet over medium-high heat, add the olive oil and chicken broth and heat until warm. Lighly whisk the egg yolks and add to the whites. Whisk just to combine and pour into the skillet. Add the ham, mozzarella and spinach pest, stirring rapidly to incorporate them into the egg mixture. Cook for 3 to 4 minutes, just until the bottom is set; the top will still be wet. Place the skillet in the oven for 5 minutes, until the frittata is firm and golden. Serve immediately or cool and serve at room temperature.