Step 1

Whisk the egg whites, milk, salt, and pepper in a medium bowl until thoroughly combined.

Step 2

Chop spinach finely and add to egg mixture.

Step 3

Melt the butter in an non-stick pan over medium heat until foaming. Add the egg mixture and stir constantly with a rubber spatula, moving the eggs around the pan until they form small curds, about 2 to 3 minutes.

Step 4

Gently shake the pan and use the spatula to spread the egg mixture evenly across the pan.

Step 5

Remove the pan from heat. Using the spatula, fold a third of the omelet over and onto itself. Gently push the folded side of the omelet toward the edge of the pan.

Step 6

Tilt the pan over the serving plate and roll the omelet onto the plate, seam side down. Serve.