01 - Whisk together eggs, milk, salt, pepper, and nutmeg until fully blended and uniform in color.
02 - Heat butter in a nonstick skillet over medium heat. Add diced shallot and cook until translucent, approximately 1–2 minutes.
03 - Add chopped spinach to the skillet and stir frequently until leaves have completely wilted, about 1 minute.
04 - Pour the egg mixture into the skillet, tilting the pan to ensure even coverage over the spinach and shallot.
05 - Cook without disturbing for 2–3 minutes until edges begin to firm. Gently lift edges with a spatula to allow uncooked egg to flow underneath.
06 - Sprinkle crumbled feta cheese evenly across one half of the omelet.
07 - Fold the omelet in half once eggs are mostly set but still slightly moist on top. Cook for 30 additional seconds, then slide onto a serving plate.
08 - Serve immediately, optionally garnished with additional feta crumbles or fresh herbs.