Special equipment: 4 (8-ounce) ramekins
Preheat the oven to 375 degrees F. Spray the ramekins with the cooking spray.
In a bowl, mix the creamed spinach to lighten it a bit, and then add the cheese. Put the egg whites into another bowl and, using an electric hand mixer, whisk them until they are able to hold stiff peaks but are still glossy. Add a third of the egg whites to the spinach and mix it in to lighten the mixture. Fold in the remaining egg whites. Divide the mixture among the ramekins. Put them onto a baking sheet and bake until they are puffed up, set, and golden brown, 25 to 30 minutes. Serve immediately.