Lightly spoon flour into a dry measuring cup; level with a knife. Combine flour and salt in a bowl. Combine milk, egg whites, and egg in a bowl; stir well with a whisk. Gradually add to flour mixture, stirring with a whisk until smooth. Place an 8-inch crepe pan or nonstick skillet over medium heat until hot. Pour a scant 1/4 cup batter into pan; quickly tilt pan in all directions so batter covers pan with a thin film. Cook about 1 to 2 minutes.
Carefully lift the edge of the crepe with a spatula to test for doneness. The crepe is ready to turn when it can be shaken loose from the pan and the underside is lightly browned. Turn crepe over, and cook for 15 seconds on other side.
Place crepe on a towel; cool. Repeat procedure until all of the batter is used, stirring batter between crepes. Stack crepes between single layers of wax paper or paper towels to prevent sticking.