Coat two baking sheets with cooking spray and a light dusting of flour. Shake off excess.
In a large mixing bowl, beat egg whites with an electric mixer until soft peak form. Gradually add sugar and beat until stiff, glossy peaks form. Gently fold in chocolate chips (setting a few aside to sprinkle onto cookies) and vanilla extract.
Drop mixture by heaping tablespoons onto prepared baking sheets about 1 inch apart, making 24 cookies (12 cookies per baking sheet). Sprinkle chocolate chips onto cookies before placing in the oven, optional.
Bake until lightly golden and no longer sticky on the surface, about 1 hour. Turn oven off and let cookies sit in oven for 1 hour. Transfer cookies to a wire rack to cool completely.