Whisk the egg whites, water, salt, and black pepper together for about 30 seconds, until lightly foamy.
Heat an 8-inch nonstick skillet over medium-low heat.
Add the olive oil or butter and coat the skillet evenly.
Pour the egg white mixture into the skillet and let it sit for about 15 seconds.
Using a silicone spatula, gently push the cooked edges toward the center of the skillet.
Tilt the skillet so the uncooked egg whites flow into the empty areas.
Continue gently folding the egg whites until soft, fluffy, opaque curds form.
Remove the skillet from the heat while the egg whites are still slightly moist to prevent overcooking.
Sprinkle with chopped chives or parsley, if using, and serve immediately.