In a small bowl, combine the 3 egg whites, 5 tablespoons (31 g) whey protein powder, 1/2 teaspoon vanilla extract, and 1 tablespoon powdered sweetener.
Whisk or blend the mixture for about 1 minute until the batter is fluffy and smooth.
Heat a nonstick 20 cm (8 inch) frying pan over medium heat and melt 1/2 teaspoon of the butter to coat the pan.
Pour half the batter into the pan, tilting and rotating the pan to spread it thinly and evenly to cover the bottom.
Cook for about 45 seconds until the bottom is lightly golden, then carefully flip with a wide spatula and cook the other side for another 45 seconds.
Repeat the process with the remaining 1/2 teaspoon butter and the remaining batter to make the second crepe.
Transfer cooked crepes to a plate and serve as desired.