1-1/2 teaspoons sherry or reduced-sodium chicken broth
1/2 teaspoon Dijon mustard
1 large egg yolk, lightly beaten
Dash cream of tartar
Let egg whites stand at room temperature for 30 minutes. Coat two 8-oz. ramekins with cooking spray and lightly sprinkle with Parmesan cheese; set aside.
In a small saucepan, melt butter. Whisk in flour, nutmeg and cayenne until smooth; gradually add milk. Bring to a boil over medium heat; cook and stir for 2 minutes or until thickened. Reduce heat; stir in the Gruyere, Camembert, sherry and mustard until cheeses are melted. Remove from heat. Transfer to a small bowl.
Stir a small amount of hot mixture into egg yolk; return all to the bowl, stirring constantly. Allow to cool slightly.
In a small bowl with clean beaters, beat the egg whites, cream of tartar and salt until stiff peaks form. With a spatula, fold egg whites into cheese mixture until combined. Transfer to prepared ramekins.
Bake at 375° for 18-22 minutes or until the top is puffed and center appears set. Serve immediately.