Yep! Try it, I promise you'll love the creamy texture. But for the most bio-available mix of amino acids blend the cooked egg whites with a dairy product such as whey powder or, as I've suggested, much cheaper cottage cheese. Sweeten with a banana or honey or even chocolate/milo etc.
I haven't done the maths on whether it's cheaper to cook pre-seperated egg whites. This recipe has been around for decades before you could buy frozen egg whites at the corner supermarket.